Method for measuring disintegration of a fibrous product
阅读说明：本技术 用于测量纤维产品的崩解的方法 (Method for measuring disintegration of a fibrous product ) 是由 克莱顿·坎贝尔 珍妮弗·赖泽 克里斯廷·威蒂克 弗兰克·齐默尔曼 于 2018-06-28 设计创作，主要内容包括：本发明提供了用于测量纤维产品的崩解的方法和系统。该方法包括将纤维产品的样品在水性溶液中崩解，任选地通过机械能进行促进，将水性溶液通过筛网以获得透过物和筛网上的保留级分，并由透过物分析至少一种参数，例如通过重量分析、光学分析、电化学分析、容量分析或其组合。其优点包括可调节性、速度和与纤维产品的实际可冲散性或再浆化性的高度相关性，以及在用于制造表现为受控崩解的纤维片(诸如可冲散或可再浆化的纤维片)的方法中的实用性。(The present invention provides a method and system for measuring disintegration of a fibrous product. The method comprises disintegrating a sample of the fiber product in an aqueous solution, optionally promoted by mechanical energy, passing the aqueous solution through a screen to obtain a permeate and a retained fraction on the screen, and analyzing at least one parameter from the permeate, e.g. by gravimetric analysis, optical analysis, electrochemical analysis, volumetric analysis or a combination thereof. Advantages include adjustability, speed, and high correlation with the actual flushability or repulpability of the fibrous product, as well as utility in processes for making fibrous sheets that exhibit controlled disintegration, such as flushable or repulpable fibrous sheets.)
1. A method for measuring disintegration of a fibrous product, comprising:
(a) at a point in time t0Immersing at least one sample of a fibrous product in an excess of an aqueous solution in a container for initiating disintegration of said sample, said sample having an initial dry weight mi，
(b) Optionally subjecting the immersed sample to mechanical energy to promote disintegration of the sample into a disintegrated sample,
(c) after a first period of time, at a point in time t1Passing an aqueous solution containing a first disintegrated sample of said fibrous product through a first screen to obtain a permeate containing a pass fraction of the disintegrated sample and a retained fraction of the disintegrated sample on said first screen, and optionally continuing to submerge any other submerged samples,
(d) analyzing the permeate from step (c) containing the pass-through fraction of the disintegrated sample for at least one parameter to obtain at least one characteristic value.
2. The method according to claim 1, wherein the obtained characteristic value is compared with a predetermined reference value, thereby determining a difference between the obtained characteristic value and the predetermined reference value.
3. The method of claim 1 or 2, wherein the analysis of the at least one parameter comprises gravimetric analysis, optical analysis, electrochemical analysis, volumetric analysis, or any combination thereof.
4. The method of claim 3, wherein the gravimetric analysis comprises:
(e) passing the permeate through a filter having a dry weight m1The filtration device of (a) to obtain a filtrate and a pass fraction of the disintegrated sample on the filtration device,
(f) drying and weighing the filter device and the pass through fraction of the disintegrated sample to obtain a weight m2And the disintegration-% of the fiber product is calculated by using the following formula:
and optionally by dividing by the basis weight, thickness, specific volume or density of the fibrous product, or by the initial sample dry weight miTo normalize the disintegration-%.
5. Method according to claim 4, wherein at a point in time t2(ii) subjecting the second disintegrated sample, and optionally at any other point in time tnSubjecting any other disintegrated sample to steps (c) to (f), and taking the obtained disintegration-% value as time (t [% ])1、t2…tn) Is plotted to obtain the disintegration rate of the fibre product.
6. The method of any one of claims 1 to 5, wherein the method is performed
(a) Ratio of characteristic value to predetermined reference value or
(b) The disintegration rate of the fiber product
Compared with corresponding values obtained from other samples or samples obtained using different process parameters.
7. The method according to any one of claims 1 to 6, wherein in step (b) the mechanical energy is generated by static mixing and/or sonication, preferably by static mixing.
8. The method according to claim 7, wherein static mixing is performed by subjecting a sample of the fiber product immersed in the aqueous solution to a rotating and/or oscillating motion.
9. The method of claim 8, wherein subjecting the sample to a rotational and/or oscillating motion is performed by mounting the container on a rotary mixer or an oscillating plane.
10. The method of any one of claims 1-9, wherein in step (c), the retained fraction of the disintegrated sample on the first screen is washed with wash water so as to wash any entrapped fines through the screen into the permeate.
11. The method of any one of claims 1-10, wherein in step (c) the first screen has a mesh size of at most 1/2", preferably at most 1/4", more preferably at most 1/8 ".
12. The method of any one of claims 1-11, wherein in step (c), the aqueous solution containing the first disintegrated sample of the fiber product is facilitated to pass through the first screen by mixing.
13. The method of any one of claims 1-12, further comprising passing parallel samples of each sample through a second screen having a mesh size smaller than the mesh size of the first screen in step (c) to obtain a parallel permeate containing a pass fraction of the disintegrated parallel sample, and a retained fraction of the disintegrated parallel sample on the second screen, followed by performing step (d) to obtain a parallel feature value.
14. The method of claim 13, wherein in step (c) said first screen has a mesh size of at most 1/2 "and said second screen has a mesh size of at most 1/8".
15. The method according to any of claims 1-14, wherein the fibrous product is a fibrous sheet, preferably a paper or a nonwoven.
16. A system for measuring disintegration of a fibrous product, wherein the system comprises:
at least one container (3) configured to receive an aqueous solution (2) and a sample (1) of a fibrous product immersed therein, the sample having an initial dry weight mi；
Optionally a unit (4) configured to subject the immersed sample to mechanical energy to promote disintegration of the sample into fragments,
a first screen (6) configured to fractionate an aqueous solution (5) containing a disintegrated sample of the fibre product into a permeate (7) containing a pass fraction of the disintegrated sample and a retained fraction (8) of the disintegrated sample on the first screen; and
at least one analysis unit (11) configured to perform an analysis of at least one parameter of the permeate (7) containing the pass fraction of the disintegrated sample to obtain at least one characteristic value, and/or
A gravimetric analysis unit comprising:
comprising having a dry weight m1A filtration unit (12) of the filtration device configured to separate the permeate (7) into a filtrate (13) and a pass fraction (14) of the disintegrated sample on the filtration device,
a drying unit (9) configured to dry the representative sample, the filtration device and a pass fraction (14) of the disintegrated sample on the filtration device, and a weighing unit (10) configured to weigh the dried representative sample to obtain miWeighing the dried filter unit to obtain m1And weighing the pass through fraction of the disintegrated sample on the dried filter unit to obtain m2And an
A processing unit (15) for obtaining disintegration-% of the fiber product by calculation:
and optionally, for the production of a fiber by dividing by the basis weight, thickness, specific volume or density of the fiber product, or by the initial sample dry weight miTo normalize the disintegration-%.
17. A method for manufacturing a fibrous sheet exhibiting controlled disintegration, comprising:
-providing an aqueous suspension comprising cellulosic fibres, non-cellulosic polymeric fibres or any combination thereof;
-draining the aqueous suspension to form a wet fibrous web and drying the wet fibrous web to obtain a fibrous sheet;
wherein at least one chemical additive contributing to the wet strength of the fibrous sheet is incorporated into the aqueous suspension or added to the wet fibrous web or the dry fibrous sheet;
-measuring the disintegration of the fibrous sheet according to the method of any one of claims 1 to 15 to obtain a characteristic value of the fibrous sheet;
-comparing the obtained value with a predetermined value; and
-adjusting the incorporation or addition of said at least one chemical additive according to the difference between said obtained value and said predetermined value.
18. A fibrous tablet exhibiting controlled disintegration obtainable by the process of claim 17.
Technical Field
The present invention relates generally to the field of fiber products, such as flushable and repulpable fiber products. More particularly, the present invention relates to a method and system for measuring disintegration of a fibrous product. Furthermore, the invention relates to a method for manufacturing a fibrous tablet exhibiting controlled disintegration.
Background
There is a continuing need in the paper industry for fibrous products that are strong enough for their intended use but still disintegrate after being discarded. Wet strength is a desirable attribute of fibrous products that come into contact with water or moisture during other processing steps or uses. Examples of such products include hygiene articles such as napkins, paper towels, household paper towels, and disposable hospital wear, as well as certain paper and paperboard grades to be coated, glued, and the like. The integrity or strength of the fibrous product is due at least in part to hydrogen bonding between the fibers. When the product is wet, water can break the hydrogen bonds and reduce the strength of the fibrous product. Untreated aggregates of cellulose fibers typically lose more than 90% of their strength when soaked in water.
To improve the integrity or strength of the fiber product, two main methods can be used. One approach is to prevent water from reaching and breaking hydrogen bonds, for example by special wet end and surface treatments such as sizing or coating. The second method is to add additives to the fiber product so that non-breaking interfiber bonds are formed, commonly referred to as permanent wet strength, or bonds that resist breaking by water, referred to as temporary wet strength. The second method is the technique of choice for most fibrous products, and involves adding a water-soluble wet strength resin to the pulp prior to forming the paper product, or adding a water-soluble wet strength resin to the wet fibrous web. So-called permanent wet strength resins (such as polyamidoamine epichlorohydrin) result in fibrous products that retain a substantial portion of their initial wet strength when placed in an aqueous medium. Some fiber products, such as toilet paper and the like, are typically discarded into septic tank systems after a short use. If the fiber product is intended or intended to be flushed or otherwise introduced into the septic tank system by municipal waste, the permanent retention of its hydrolytic resistance properties may cause the system to clog. Similarly, for fibrous products to be recycled, too high a permanent wet strength is not desirable, as repulping would require harsh conditions and a large amount of energy. Flushability or repulping is the primary reason manufacturers are increasingly using temporary wet strength additives that provide wet strength sufficient for their intended use, but then decay upon contact with water. The decay in wet strength helps to disintegrate more easily during repulping or when flushed through municipal waste or into septic tank systems. Processes for providing fibrous products having good initial wet strength and which decay significantly with time are constantly being developed.
Flushability is a major problem with many fibrous products, such as nonwovens. In particular, wipes often clog pipes and pumps in municipal wastewater systems. INDA (international non-woven fabric industry association) has been working with wipe manufacturers, wastewater treatment plants, and local government officials to address this growing problem and has provided a stirred tank disintegration test for evaluating the likelihood of a product disintegrating when subjected to mechanical agitation in water or wastewater. The development of new technologies and fiber sources is ongoing to provide fiber products that can be flushable but still meet the high quality requirements of the intended use.
Not all fiber products labeled as flushable are truly dispersible because they do not disperse well under all conditions encountered in toilet and septic systems. Many of the fibrous products marked as flushable are flushable simply because they are small in size, i.e., they are small enough to pass through a piping system without clogging. However, they do not necessarily break down into smaller pieces or fiber clusters, or break down only to a small extent. For example, almost all products that claim to be flushable can pass the INDA flushability guidelines and even the agitated tank disintegration test, but only a few of them are truly dispersible because they do not disperse sufficiently to pass smaller pipes and other types of restrictions in sewage treatment systems. Thus, even if such fiber products pass through the piping system immediately after being dispersed, they can clog sewage systems and effluent clarifiers controlled by municipal/municipal systems.
Other disadvantages of the INDA stir chamber disintegration test are that it has multiple steps and takes several hours or even a day to obtain a result, and the result only indicates pass/fail information, giving little or no information about, for example, dispersion into individual fibers, fines or bundles of fibers or speed of disintegration.
Despite the ever-increasing demand, there are still very few techniques available for measuring or verifying the disintegration rate of fibrous products. Accordingly, there is a need for a reliable and simple method for measuring disintegration of a fibrous product that does not require complex or expensive equipment and is capable of providing a quick pass/fail indication of dispersibility, a quantitative indication of disintegration, and/or a disintegration rate.
Disclosure of Invention
It is an object of the present invention to minimize or even eliminate the drawbacks of the prior art.
It is a further object of the invention to provide a reliable method for measuring the disintegration of a fibre product.
It is a further object of the present invention to provide a system for measuring disintegration of a fibre product.
It is another object of the present invention to provide a method for manufacturing a fibrous sheet exhibiting controlled disintegration, using which method for measuring the disintegration of a fibrous product according to the present invention.
These objects are achieved by the present invention having the characteristics set forth in the characterizing part of the appended claims.
Preferred embodiments of the invention are set forth in the dependent claims.
The present invention helps to reliably evaluate the disintegration ability of a fiber product in an aqueous medium, and more specifically the dispersibility thereof. Furthermore, using some embodiments of the present invention, it is possible to assess whether the fiber product disintegrates into fragments on a macroscopic scale, i.e. breaks into relatively large fragments, or into fragments on a microscopic scale, i.e. disperses into fiber bundles or individual fibers, thereby improving the evaluation and understanding of the disintegration of the fiber product. This is particularly useful in developing or manufacturing truly flushable and repulpable fiber products, which would provide substantial savings in reducing toilet, plumbing, storage tank or septic tank blockages, reducing operational malfunctions, improving yields in repulping of recycled and shredded paper, and reducing environmental pollution (e.g., land disposal).
Other advantages of the invention are described and exemplified in the following figures and detailed description. The embodiments and advantages mentioned in this description relate, where applicable, to the method, system, process and fibre sheet according to the invention, although not always specifically mentioned.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate some embodiments of the invention and together with the description help to explain the principles of the invention. In the drawings:
figure 1 shows the disintegration-% and turbidity of the sieved permeate of a towel sample as a function of static mixing time.
Figure 2 shows the disintegration-% and turbidity of the sieved permeate of a towel sample as a function of static mixing speed.
Figure 3 shows the disintegration-% and turbidity of the sieved permeate for the tissue and towel samples compared to the wheel and shaking table (shaker).
Figure 4 shows the disintegration-% and turbidity of the sieved permeate of a towel sample when using a vertical mixing wheel (left most) and a shaking table (shaker) with increased static mixing speed for 30min (60 min except for the 400rpm shaker).
Fig. 5a shows the variation of disintegration-% over time (h) using 26rpm of the mixing wheel and 100rpm of the Britt jar for the 2-ply bath towel S3 while sieving through a 1/4 "screen and using a 1/16" screen in parallel, and fig. 5b shows the same for the 2-ply bath towel S2.
Figure 6 shows the variation of disintegration-% over time (h), for four 2-ply bath tissues, 26rpm of the mixing wheel was used, and no mixing while sieving through the 1/2 "screen. Demonstrating the effect of permanent or temporary or no wet strength agents.
Figure 7 shows the disintegration-% as a function of time (h), for three 2-ply tissues, 40rpm using a mixing wheel, and no mixing, while sieving through an 1/4 "screen.
Fig. 8 is a flowchart illustration of a system according to some embodiments of the inventions.
Detailed Description
The inventors have surprisingly found that disintegration, which has been shown to be associated with flushability and repulpability of fibre products, can be measured in a reliable manner by the method of the invention. Furthermore, it has been found that the measurement method can be used for controlling disintegration, for example monitoring flushability and repulping properties of a fibrous sheet when producing the fibrous sheet.
By flushable, it is generally meant that the fibrous product can be discarded by a sanitary device, such as a toilet, without clogging or otherwise interfering with the disposal process. The current standard for flushability is set by the third edition INDA/EDANA guidelines for flushability evaluation of disposable nonwoven products (method for evaluating compatibility of disposable nonwoven products with pipelines and sewage facilities) (
By disintegration is meant the process in which the fibrous product weakens, loses its integrity and breaks into smaller parts. Generally, it is operationally defined by the loss of quality of the product after exposure to specific environmental conditions. Disintegration may be due to dissolution of soluble ingredients, chemical or biological degradation of constituents in the product, physical forces that break the product into smaller products, or a combination of the above factors.
By dispersion is meant a disintegration process characterised by the breaking of the substance into fine fragments which are separated from each other and more or less evenly distributed in the water. The dispersibility of the fibre product can be seen as the disintegration of the fibre product into fibre bundles and/or individual fibres and fines.
Generally, a product is considered dispersible if it passes the agitated tank disintegration test specified in INDA FG 502. While disintegration and dispersibility refer to the breakdown of the product, disintegration is a broader term relating to both macroscopic and microscopic disintegration and breakdown of the product, and dispersibility refers to the physical separation of the product into fine fragments. Thus, any method that does not directly measure the dispersion fraction may not be sufficient to evaluate the true dispersion of the fiber product.
Typical methods for measuring the disintegration of a fibrous product include:
(a) at a point in time t0Immersing at least one sample of the fibrous product in an excess of aqueous solution in a container for initiating disintegration of the sample(s), the sample having an initial dry weight mi，
(b) Optionally subjecting the immersed sample(s) from step (a) to mechanical energy to promote disintegration of the sample(s) into disintegrated sample(s),
(c) after a first period of time, at a point in time t1Passing an aqueous solution containing a first disintegrated sample of the fibre product, i.e. the sample from step (a) or (b), through a first screen to obtain a permeate containing the passed fraction of the disintegrated sample and a retained fraction of the disintegrated sample on the first screen, and optionally continuing to submerge any other submerged sample(s),
(d) analyzing at least one parameter of the permeate containing the pass fraction of the disintegrated sample from step (c) for obtaining at least one characteristic value, and optionally by dividing by the basis weight, thickness, specific volume or density of the fibrous product, or by the initial sample dry weight miTo normalize the characteristic values.
Optionally, the obtained characteristic value is compared with a predetermined reference value, thereby determining a difference between the obtained characteristic value and the predetermined reference value. The predetermined reference value may correspond to, for example, a known property, such as disintegration-%.
The method of the invention facilitates the determination of a characteristic value related to, for example, the level of disintegration, or a time series of characteristic values representing, for example, the disintegration rate of a fibrous product. In the measurement of the disintegration rate or disintegration curve, it is necessary at the point in time t0Submerging all samples, and continuing to submerge the samples until at the desired point in time t1、t2…tnThe separation of the fractions described in step (c) is performed. Since any larger solids are collected on the screen, the accuracy of the permeate analysis can be improved and the margin of error reduced, especially when optical analysis is used. In addition, it can be evaluated whether the fiber product disintegrates into fragments only on a macroscopic scale, i.e. breaks into relatively large fragments which remain on the screen, or whether the disintegration into fragments also or even mainly involves the dispersion into fiber bundles or individual fibers and fines which pass through the screen into the permeate. Such an assessment is of significant value in obtaining an improved assessment and understanding of the flushability or repulping properties of the fibrous product.
In some embodiments, the time series or disintegration level of characteristic values, e.g. disintegration speed, of a fibrous product is compared with corresponding values obtained from other samples, such as tissues of different quality, or samples obtained using different process parameters. In some embodiments, the ratio of the characteristic value to a predetermined reference value or said disintegration rate of the fibrous product is compared with corresponding values obtained from other samples or samples obtained using different process parameters. These allow identification and modification of the process (process parameters) to obtain enhanced dispersion of the fiber product. In some embodiments, the analysis of the at least one parameter comprises gravimetric analysis, optical analysis, electrochemical analysis, volumetric analysis, or any combination thereof. Preferably, the analysis comprises at least a gravimetric analysis, as its accuracy and quantification shows the actual degree of disintegration.
In some embodiments, the gravimetric analysis comprises:
(e) passing the permeate from step (c) through a filter having a dry weight m1The filtration device of (a) to obtain a filtrate and a pass fraction of the disintegrated sample on the filtration device,
(f) drying and weighing the filtration device and the pass through fraction of the disintegrated sample to obtain a weight m2And the disintegration-% of the fiber product is calculated by using the following formula:
and optionally by dividing by the basis weight, thickness, specific volume or density of the fibrous product, or by the initial sample dry weight miTo normalize disintegration-%.
In some embodiments, the characteristic value or disintegration-% is normalized by dividing by the basis weight, thickness, specific volume or density of the fiber product, especially when the fiber product is a fibrous sheet, as this may improve the accuracy of the measurement method. This is because basis weight, thickness (thickness), specific volume (specific volume) and density (specific gravity) all relate to information about the volume of the fibrous product which has an effect on disintegration.
Some particular methods for measuring disintegration of a fibrous product according to the invention include:
(a) at a point in time t0Immersing at least one sample of the fibrous product in an excess of aqueous solution in a container for initiating disintegration of the sample(s), the sample having an initial dry weight mi，
(b) Optionally subjecting the immersed sample(s) to mechanical energy to promote disintegration of the sample(s) into disintegrated sample(s),
(c) after a first period of time, at a point in time t1Passing an aqueous solution containing a first disintegrated sample of the fibre product through a first screen to obtain a permeate containing a pass fraction of the disintegrated sample and a retained fraction of the disintegrated sample on the first screen, and optionally continuing to submerge any other submerged sample(s),
(d) gravimetrically analyzing the permeate containing the pass fraction of the disintegrated sample from step (c) to obtain disintegration-% of the fiber product, wherein the gravimetrically analyzing comprises
(e) Passing the permeate through a bed with a dry weight of m1The filtration device of (a) is subjected to filtration to obtain a filtrate and a pass fraction of the disintegrated sample on the filtration device,
(f) drying and weighing the filtration device and the pass through fraction of the disintegrated sample to obtain a weight m2And the disintegration-% of the fiber product is calculated by using the following formula:
and optionally by dividing by the basis weight, thickness, specific volume or density of the fibrous product, or by the initial sample dry weight miTo normalize disintegration-%.
In some embodiments, non-gravimetric analysis may be used in addition to or in place of gravimetric analysis, as non-gravimetric analysis may be faster and less labor intensive, e.g., involving only the use of a single automated detector. These analyses may yield sufficiently accurate information about disintegration or dispersibility, in particular of the pass/fail type, or even quantitative information, in particular when a calibration curve has been prepared, for example by plotting the instrument response curve against the disintegration-% (optionally normalized). Preferably, the non-gravimetric analysis is used in addition to gravimetric analysis.
Some other methods for measuring disintegration of a fibrous product according to the present invention include:
(a) at a point in time t0Immersing at least one sample of the fibrous product in an excess of aqueous solution in a container for initiating disintegration of the sample(s), the sample having an initial dry weight mi，
(b) Optionally subjecting the immersed sample(s) to mechanical energy to promote disintegration of the sample(s) into disintegrated sample(s),
(c) after a first period of time, at a point in time t1Passing an aqueous solution containing a first disintegrated sample of the fibre product through a first screen to obtain a permeate containing a pass fraction of the disintegrated sample and a retained fraction of the disintegrated sample on the first screen, and optionally continuing to submerge any other submerged sample(s),
(d) subjecting the permeate containing the pass fraction of the disintegrated sample from step (c) to at least one non-gravimetric analysis, preferably an optical analysis, an electrochemical analysis, a volumetric analysis or any combination thereof, to obtain at least one characteristic value of the fiber product, more preferably to an optical analysis of the permeate to obtain a turbidity of the permeate,
and comparing the obtained characteristic value with a predetermined reference value, the predetermined reference value corresponding to, for example, a known property such as disintegration-%, to determine a difference between the obtained characteristic value and the predetermined reference value.
The fibrous product may be any fibrous product or portion thereof, including (as a coherent assemblage) cellulosic fibers, non-cellulosic polymeric fibers, or any combination thereof. In some embodiments, the fibrous product comprises or consists essentially of cellulosic fibers. In other words, the fiber product may comprise at least 80% (w/w), at least 90% (w/w), at least 95% (w/w), at least 98% (w/w), 99% (w/w) and even 100% (w/w) cellulose fibers, based on the dry weight of the fiber product. Examples of fibrous products include paper products, nonwovens, tampons, tampon holders, diapers, tampons, liners, medical dressings, molded articles (such as transport packaging or sponges). Examples of paper products include paper towels, hand towels, printing paper, writing paper, paperboard, cardboard, corrugated, shredded, recycled paper, bath paper, and the like. Examples of nonwovens include sanitary wipes, household cleaning wipes, towels, and the like. Cellulose fibres mean any cellulose or lignocellulose fibres separated, for example, from wood, cotton, flax, hemp, jute, ramie, kenaf, abaca or sisal, or fibres such as manmade fibres, lyocell, viscose regenerated cellulose. Typically, cellulosic fibers include pulp fibers obtained by chemical pulping such as kraft or sulfite pulping, mechanical pulping, thermomechanical pulping, chemithermomechanical pulping, or organosolv pulping. The cellulose fibers may be bleached. In addition to or instead of cellulosic fibres, the fibrous product may comprise non-cellulosic polymeric fibres, such as fibres of polyethylene, polypropylene or polyester, for example in the form of mono-or bicomponent fibres. In some embodiments, the fiber product may comprise, or consist essentially of, based on the dry weight of the fiber product: at least 80% (w/w), at least 90% (w/w), at least 95% (w/w), at least 98% (w/w), 99% (w/w) and even 100% (w/w) of non-cellulosic polymeric fibres. The fibrous product may also include dry strength resins, wet strength resins, softeners, binders, fillers, pigments, inks, or other substances that may resist or slow the disintegration of the fibrous product. In some embodiments, the fiber product comprises at most 10% (w/w), or at most 5% (w/w), or at most 3% (w/w) of the additive, based on the dry weight of the fiber product.
In some embodiments, the fibrous product is a fibrous sheet, preferably a paper product or a nonwoven. In some embodiments, the fibrous product is a fibrous web formed in the manufacture of paper or paperboard or a residue thereof. The web may contain process water ("wet web") or be substantially dry. These fiber products represent the largest group of products that require reliable methods and systems to measure disintegration and evaluate the flushability and repulping properties of these products. The method and system are useful for developing dispersible products such as flushable or repulpable paper products and nonwovens.
Conveniently, the fiber product is cut into pieces or samples of similar size, e.g., 1 "x 1" or 2 "x 2" or 3 "x 3", etc., for testing and comparison prior to immersion in an excess of aqueous solution. One sample may comprise two or more subsamples of the fibre product. Preferably, the initial dry weight m of the sample is determined for at least one additional sampleiAnd for all samples of the same product batch and the same size. This is because drying may result in solidification or cornification of the sample, which may have an effect on disintegration or dispersibility of the sample. The aqueous solution may be any aqueous solution, such as deionized water, but is preferably tap water, to better simulate actual washout conditions. Excess means an amount which is not completely absorbed by the sample of the fibrous product, but which covers it and allows it to float. The amount of the fiber product (amount of the sample of the fiber product) may be less than 50% (w/w) of the aqueous solution, such as at most 30% (w/w), or at most 20% (w/w), or at most 10%, or at most 5% (w/w) of the aqueous solution. In some embodiments, the accuracy of the measurement may be improved, e.g. better simulating washout conditions, if the amount of the sample of the fiber product is at most 3% (w/w), or even at most 1% (w/w) of the aqueous solution.
The container may be any container or vessel suitable for receiving a sample of the fibrous product and an aqueous solution and is subjected to mechanical energy upon application of the mechanical energy. It may have any shape and be any suitable material. Preferably, the container is sealable and may be sealed at any step of the method, particularly when mechanical energy is applied, for example by a cap, lid or cover plate, to prevent spillage. In some embodiments, the container includes built-in elements, such as baffles or plates, inside that further promote disintegration.
The screen may be any suitable screen, such as a perforated plate or a screen, comprising at least one opening, preferably a plurality of openings, to avoid slowing down the screening and clogging the screen. The opening may be of any shape. In some embodiments, the screen has a mesh size of up to about 1", but preferably up to about 1/2", which passes through loose fibers, fines, fiber bundles, and large pieces of the sample; or a mesh size of up to about 1/4 "which passes through loose fibers, fines, fiber bundles, and small pieces of the sample; or a mesh size of up to about 1/8 "that passes through the loose fibers and fines of the sample. For example, the screen may have a mesh size in the range of about 0.053 "to about 1", preferably about 1/16 "to about 1/2", or about 1/16 "to about 1/4". Mesh sizes of about 1 "or about 1/2" through larger pieces can be too large in most cases for the evaluation of dispersibility. However, such screens may be useful in evaluating or quantifying how the disintegration of the fibrous product is proceeding, especially in embodiments where at least two screens of different mesh sizes are used. It is therefore noted that the use of larger sample sizes (width/diameter of the solid sample) may be necessary. Suitable sample size (width/diameter): mesh size ratios, such as bath tissue, may be between 4:1 and 10:1, or between 6:1 and 8: 1. The sample size (width/diameter of the solid sample) may be between 400% and 1000%, or between 600% and 800%, respectively, of the mesh size. The sample size (width/diameter of the solid sample) may be at least 300%, preferably at least 400%, more preferably at least 500% of the mesh size. A mesh size of up to about 1/4 "may be optimal, for example, for evaluating flushability of a fibrous product. A mesh size of at most about 1/8 "or even at most about 1/16" may be optimal, for example, for evaluating repulpability of a fiber product, since yield of individual fibers is important to minimize discard volume. As used herein, mesh size refers to the size of the openings of a screen (in inches).
Increasing the introduction of mechanical energy (e.g., higher revolutions per minute) generally increases the dispersion speed and allows for the use of smaller mesh sizes and/or shortens the dispersion time. In some embodiments, the immersed sample(s) are subjected to mechanical energy to facilitate disintegration of the sample(s) into fragments to better simulate the washout or repulping conditions and to reduce the time required to carry out the method. However, it is known that fiber products are easily dispersible and may not need to be subjected to mechanical energy at all. Suitably, the test conditions are compatible with the actual conditions of use, such as dispersion or repulping. In dispersion, the mechanical energy is generally low and the product should disintegrate to allow dispersion without clogging. In repulping, the energy should be sufficient to disintegrate and disperse the application without damaging the fibers and thus impairing the properties of the recycled product to be formed.
In physical science, mechanical energy is the sum of potential energy and kinetic energy. Which is the energy associated with the motion and position of the object. Subjecting the immersed sample(s) of the fibrous product to mechanical energy to promote disintegration of the sample(s) into fragments may be accomplished by any device capable of causing movement and/or change in position of the sample(s) immersed in the aqueous solution. Examples of suitable devices include static mixers, dynamic mixers, and sonic processors, such as ultrasonic processors.
In some embodiments, the mechanical energy in step (b) is generated by static mixing and/or sonication, preferably by static mixing. Both ultrasonic and static mixing provide gentle mixing to avoid excessive shear forces. In this way, disintegration testing may provide a more reliable indication of the flushability of the fibre product, noting the relatively gentle flow in the waste water system. Static mixing is preferred because the energy level can be easily adjusted and practical results show that static mixing is more effective in promoting disintegration than sonication. In addition, static mixing better simulates the swirling and agitating motion of the fiber product being dispersed through the waste water piping system.
In some embodiments, static mixing is performed by subjecting a sample(s) of the fiber product immersed in the aqueous solution to a rotational and/or oscillatory motion. This may be achieved in any suitable manner, but preferably the container(s) are mounted to the rotary mixer or the oscillation plane, for example by using clamps or other fixing means. The oscillation plane may be arranged to be inclined, for example, from side to side, or to provide horizontal circular or elliptical oscillations or oscillations. Preferably, the oscillation plane is an oscillation table. The impeller may rotate the container holding the submerged sample horizontally, vertically or obliquely. In some embodiments, the rotary mixer is a wheel, roller bottle or drum mixer, preferably a wheel.
The mechanical energy may also be generated by a dynamic mixer. However, noting the relatively smooth flow in the wastewater system, the action of the dynamic mixer may create so strong shear forces on the fiber product that disintegration testing provides an overly optimistic impression of the disintegration capabilities (such as flushability) of the product. On the other hand, dynamic mixing may be a more suitable option in order to evaluate the repulping properties of the fiber product. In some embodiments, the mechanical energy in step (b) is generated by dynamic mixing, for example using a stirrer, a blender or a rotor stator type mixer.
In some embodiments, at least one chemical is added to the aqueous solution during step (a) and/or (b). In this way, the effect of chemicals on disintegration properties (such as disintegration-% or speed) can be evaluated when the fibre product is in contact with water, for example if an improved repulping process is being developed, or the effect of these chemicals in septic tank or toilet flushing water is being investigated. Other conditions, in particular during steps (a) and/or (b), such as temperature or pressure, may also be varied, for example to assess their effect on the efficiency of the repulping.
In some embodiments, in step (c), the retained fraction of the disintegrated sample on the first screen is washed with wash water so as to wash any entrapped fines through the screen into the permeate. This can be done by flushing the retained fraction on the screen with rinsing water. However, this may not be effective in reducing entrapment of fibers and fines, as these may still remain in the clumped and folded larger pieces. Preferably, the washing step is carried out by resuspending the retained fraction in washing water and passing the resuspended retained fraction through a sieve. These embodiments may provide improved accuracy because the entrapment of fibers and fines by larger debris retained on the screen may be minimized. Preferably, the rinsing step is performed at least twice to further improve accuracy.
In some preferred embodiments, in step (c), the aqueous solution containing the first disintegrated sample of fiber product is further diluted with water and then passed through a first screen. In these embodiments, the sample size of the fiber product may be at most 3% (w/w) or at most 1% (w/w), or even at most 0.1% (w/w) of the aqueous solution comprising the dilution water. Alternatively or additionally, in some embodiments, the aqueous solution containing the first disintegrated sample of fibrous product in step (c) is passed through a first screen with gentle agitation so that the sample pieces are evenly suspended throughout the screening process. All of these embodiments may provide improved accuracy of the measurement method, as the disintegrated debris comprising fibers and fines may be more evenly suspended, thereby minimizing entrapment of fibers and fines by larger debris remaining on the screen.
In some embodiments, any residue of the disintegrated sample of the fibrous product is rinsed from the container with rinsing water and passed through the first screen. In this way, the accuracy of these embodiments may be further improved.
In some embodiments, in step (c), the aqueous solution containing the first disintegrated sample of fibrous product is promoted to pass through the first screen by mixing. Mixing may be performed by any mixing device, such as by an impeller over a screen, to keep disintegrating fragments, including fibers and fines, in motion and thus more uniformly suspended as they pass through the screen. A preferred type of equipment for facilitating the passage of the aqueous solution through the first screen by mixing is a Britt tank equipped with a screen and impeller of suitable mesh size. These embodiments may further improve the accuracy of the measurement method, as the entrapment of fibers and fines by larger debris may be minimized.
In some embodiments, the second disintegrated sample, and optionally any other disintegrated sample, is subjected to steps (c) to (f) at time point t2 and the obtained disintegration-% value is taken as time (t)%1、t2…tn) Function of (2)Plotting is done to obtain the disintegration rate of the fibrous product. These embodiments are particularly beneficial when it is important to understand the disintegration of the fibrous product over time, for example in order to identify products that exhibit delayed disintegration.
In some embodiments, the method further comprises passing the parallel sample of each sample through a second screen having a mesh size smaller than the mesh size of the first screen in step (c) to obtain a parallel permeate containing a pass fraction of the disintegrated parallel sample and a retained fraction of the disintegrated parallel sample on the second screen, followed by step (d) to obtain a parallel feature value. Some of these embodiments may further comprise steps (e) and (f) for obtaining parallel disintegration-% of the fiber product. In this way, it is possible to evaluate and quantify how the disintegration of the fibre product has taken place. For example, a characteristic value of the sample, such as disintegration-%, may represent the total disintegration of the fiber product, including macro-scale disintegration; and parallel characteristic values, such as parallel disintegration-%, may represent micro-scale disintegration into free fibers and fines only. In principle, it is also possible to arrange a plurality of screens of decreasing mesh size in succession in order to evaluate the same sample.
Disintegration-% may be related to the actual flushability or repulpability of the fiber product, or safe disintegration of the fiber product. This correlation may depend on the type of fibrous product and may be different for paper towels and hand towels, for example. Furthermore, the presence of any chemical additives incorporated into the aqueous suspension or added to the wet web or dried fibrous sheet that contribute to the wet strength of the fibrous sheet may have a significant effect on disintegration-%. As known to those skilled in the art, there are several known factors that affect the disintegration properties of the fibrous product, such as furnish type, process chemistry, and temporary wet strength. By appropriate selection of the analysis method and the parameters to be analyzed, information about these known factors can be obtained, or new factors influencing the disintegration properties can be determined.
In some embodiments, the permeate containing the pass through fraction of the disintegrated sample from step (c) is subjected to an analysis of at least one parameter to obtain at least one characteristic value, wherein the analysis of at least one parameter comprises an optical analysis, an electrochemical analysis, a volumetric analysis or any combination thereof. In particular, an analysis comprising detection by a detector may provide a quick pass/fail indication of flushability or repulping, for example when comparing the obtained characteristic value with a predetermined reference value corresponding to, for example, a known disintegration-%. When the analysis includes one of these analyses, the method may provide further information, for example information about the disintegration mechanism. The parameter may be, for example, turbidity, particle size, charge density, alkalinity or conductivity. In a preferred embodiment, the parameter is turbidity and the analysis is an optical analysis, for example performed with a turbidimeter, a nephelometer, a turbidimeter, a photometer, an ultraviolet-visible spectrophotometer, a laser turbidimeter, a reflectometer, a fiber optic system or an optical back-scatter sensor (OBS), preferably a turbidimeter. For a permeate obtained using a screen with a mesh size of at most 1/8", preferably at most 1/16", i.e. a permeate that does not contain large debris, optical analysis can provide accurate results. High levels of recycled fiber material in fiber products can provide increased values in optical analysis, and thus optical analysis can be used to identify such products. The turbidimeter directly measures the intensity of light (typically at 90 ° in the beam direction) scattered by suspended particles (here fragments of the fiber product sample), the intensity being proportional to the amount of suspended particles in the light path. A nephelometer generally provides better accuracy and sensitivity than a nephelometer and can be beneficial for low turbidity solutions containing small particles. A turbidimeter measures the intensity of light after passing through the solution and quantifies the amount of light transmitted remaining. A turbidimeter may be beneficial for relatively turbid solutions where the scattering particles are large relative to the wavelength of light used. A turbidimeter may comprise a measurement system for side scattered (typically at 90 °), optionally forward scattered and transmitted light, obtaining a turbidity value as a ratio of the 90 ° signal to the transmission value or to the sum of the forward scattered and transmission values. Turbidimeters may be beneficial for solutions of intense and/or various colors, or solutions of high turbidity, such as fiber products containing large amounts of recycled fiber material. Uv-vis spectrophotometers may be used for optical detection by measuring the absorption of light by suspended particles at a fixed wavelength or over a full spectrum. OBS monitors solution turbidity by backscattering of pulsed infrared light emitted from the OBS measuring head. All of these optical assays are easy to perform and provide rapid and accurate detection. Regardless of the type of optical analysis used, the device for measuring turbidity using optical analysis is hereinafter referred to generically as a turbidimeter.
In some embodiments, some or all of the permeate from step (c) containing the pass fraction of the disintegrated sample may be routed to analysis by a detector, such as a turbidimeter (e.g., by measuring a flow cell of a turbidimeter) to detect at least one parameter of the aqueous solution or dispersed fragments of the disintegrated sample.
In addition to the analysis of the permeate from step (c) containing the pass through fraction of the disintegrated sample, the retained fraction of the disintegrated sample on the screen may also be analyzed. For example, when the permeate is analyzed to provide a rapid pass/fail indication, the retained fraction can be subjected to a more time-consuming gravimetric analysis.
Referring to fig. 8, an exemplary system for measuring disintegration of a fibrous product includes:
at least one
Optionally a
a
at least one
A gravimetric analysis unit comprising:
comprising having a dry weight m1Filter unit 12 of the filter deviceConfigured to separate the
a
A
and, optionally, for the production of a fiber by dividing by the basis weight, thickness, specific volume or density of the fiber product, or by the initial sample dry weight miTo normalize disintegration-%.
In some embodiments,
In some embodiments, the means for static mixing is configured to produce a rotational and/or oscillating motion and comprises a clamp(s) for mounting the container(s).
In some embodiments, the device for static mixing is an oscillating planar or rotating mixer.
The filter device may be any filter device designed for this purpose, such as filter paper, to constitute a filter unit together with e.g. a buchner funnel and a vacuum flask. The filtration device collects the pass through fraction of the disintegrated sample from step (c) of the method.
In some embodiments, the at least one
A typical process for making fibrous sheets exhibiting controlled disintegration, such as flushable or repulpable fibrous sheets, comprises: providing an aqueous suspension comprising cellulosic fibers, non-cellulosic polymeric fibers, or any combination thereof; draining the aqueous suspension to form a wet fibrous web, and drying the wet fibrous web to obtain fibrous sheets; wherein at least one chemical additive contributing to the wet strength of the fibrous sheet is incorporated into the aqueous suspension or added to the wet fibrous web or the dry fibrous sheet; measuring the disintegration of the fiber sheet according to the method of the present invention to obtain a characteristic value of the fiber sheet; comparing the obtained value with a predetermined value; and adjusting the incorporation or addition of at least one chemical additive according to the difference between the obtained value and the predetermined value.
One or more measurements may be taken periodically or occasionally during the manufacturing process of the fibrous sheet, for example as a quality control. Methods for manufacturing fibrous sheets exhibiting controlled disintegration may particularly benefit from methods that measure disintegration using rapid analysis, such as optical analysis.
The chemical additive may be any chemical additive that contributes to the wet strength of the fibrous sheet, alone or in combination with other chemical additives. Examples of chemical additives that contribute to the wet strength of the fibrous sheet include wet strength agents such as permanent or temporary wet strength agents, degrading agents, wet strength decay enhancing agents, or dry strength agents.
The predetermined (reference) value refers to e.g. a disintegration-% or turbidity value that is expected to be related to e.g. a desired level of dispersability or flushability or repulping of a certain type of fibre product. Such predetermined values may be determined, for example, by creating a correction curve.
A difference between the value obtained and a predetermined value may trigger, for example, a reduction in the amount of wet strength agent to be used if the value detected does not reach a predetermined value related to the dispersibility; or if the values examined indicate a very high dispersibility potential, the amount of wet strength agent used is increased so as not to impair the strength level required for the intended use.
The present invention also relates to fibrous sheets exhibiting controlled disintegration, such as flushable or repulpable fibrous sheets, obtainable by a method according to one or more embodiments of the present invention.
Any of the particular features or characteristics of the embodiments of the invention or described in this specification may be combined with each other in whole or in part. Even several embodiments or specific features or characteristics may be combined together, in whole or in part, to form further embodiments of the invention. Such modifications and variations are intended to be included within the scope of the present invention. The methods, systems, processes, or fibrous sheets to which the present invention relates may include at least one embodiment of the present invention described in this specification.
Some embodiments of the invention will be described in more detail below with reference to the accompanying drawings. The present invention is disclosed in detail below with respect to some embodiments and examples thereof, which enable one skilled in the art to utilize the invention. Not all steps of an embodiment are discussed in detail, as many steps will be apparent to those of skill in the art based on this description.
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