阅读说明：本技术 一种胶合板用无甲醛胶粘剂及其制备方法 (Formaldehyde-free adhesive for plywood and preparation method thereof ) 是由 朱玉国 赵康 李炳泉 唐立超 董春生 滕时飞 于 2021-08-18 设计创作，主要内容包括：本申请公开了一种胶合板用无甲醛胶粘剂。所述胶合板用无甲醛胶粘剂产品分由主剂和交联剂组成,所述的主剂包括：水性乳液、多元醇缩水甘油醚、填料、助剂、水。本发明所述的胶合板用无甲醛胶粘剂产品本身无甲醛释放,适用期及开口时间长,粘结性好,可以在完全不改变胶合板行业现有成熟制备产线及工艺的情况下来制备胶合板,得到的胶合板无甲醛释放,克服了现有无甲醛胶粘剂在应用到胶合板行业中性能、工艺、环保性等方面无法兼顾的缺点。(The application discloses a formaldehyde-free adhesive for plywood. The formaldehyde-free adhesive product for the plywood comprises a main agent and a cross-linking agent, wherein the main agent comprises: water-based emulsion, polyhydric alcohol glycidyl ether, filler, auxiliary agent and water. The formaldehyde-free adhesive product for the plywood disclosed by the invention has the advantages of no formaldehyde release, long working life and opening time and good cohesiveness, can be used for preparing the plywood under the condition of not changing the existing mature preparation production line and process in the plywood industry, does not release formaldehyde in the obtained plywood, and overcomes the defect that the performance, process, environmental friendliness and the like of the existing formaldehyde-free adhesive applied to the plywood industry cannot be taken into consideration.)

1. The formaldehyde-free adhesive for the plywood is characterized by comprising a main agent and a cross-linking agent, wherein the main agent comprises: water-based emulsion, polyhydric alcohol glycidyl ether, filler, auxiliary agent and water; the polyol glycidyl ether is an oligomer with a main chain containing ether bonds (-R-O-R-), and a terminal group or a side group containing more than 2 hydroxyl groups (-OH).

2. The formaldehyde-free adhesive for plywood according to claim 1, wherein the aqueous emulsion is 20 to 40 parts; 50-100 parts of water; 10-20 parts of polyhydric alcohol glycidyl ether; 30-70 parts of a filler; 5-10 parts of a thickening agent; 0.1-0.5 part of defoaming agent; 0.2-0.5 part of dispersant; 6-40 parts of a cross-linking agent.

3. The formaldehyde-free adhesive for plywood as claimed in claim 1, wherein said aqueous emulsion is a product obtained by polymerizing a monomer and water at a certain temperature under the action of an emulsifier and an initiator, and comprises: vinyl acetate-ethylene co-cluster water-based emulsion, polyvinyl acetate water-based emulsion, acrylic polymer emulsion and rubber water-based emulsion.

4. The formaldehyde-free adhesive for plywood as claimed in claim 1, wherein said aqueous emulsion is an emulsion containing no benzene-based monomer.

5. The formaldehyde-free adhesive for the plywood as recited in claim 1, wherein the pH value of the aqueous emulsion is 4-8; the Tg of the emulsion is between-20 and 25 ℃.

6. The formaldehyde-free adhesive of claim 1 wherein the glycidyl ether of a polyol is a glycerol polyether comprising: glyceryl polyether-7; glyceryl polyether-8; glyceryl polyether-12; glyceryl polyether-15; glyceryl polyether-18; glyceryl polyether-20; glyceryl polyether-26; glyceryl polyether-31.

7. The formaldehyde-free adhesive for plywood of claim 1 wherein said filler is: one or more of calcium carbonate, barium sulfate, white carbon black, pottery clay, gypsum powder, talcum powder, starch, flour and wood powder.

8. The formaldehyde-free adhesive for the plywood as claimed in claim 1, wherein the defoaming agent is a polyether defoaming agent, has a molecular weight of not less than 3000, has a hydroxyl functional group of not less than 3, and has a solubility of not less than 5 g/L.

9. The formaldehyde-free adhesive for plywood of claim 1 wherein said cross-linking agent is: toluene Diisocyanate (TDI), diphenylmethane diisocyanate (MDI), polymeric diphenylmethane diisocyanate (pMDI), isophorone diisocyanate (IPDI), Hexamethylene Diisocyanate (HDI).

10. The method for preparing the formaldehyde-free adhesive for the plywood as claimed in claim 1, wherein water, a dispersing agent and a defoaming agent are sequentially added into a disperser and stirred for 3-5min, then a filler is added and stirred for 15-20min, and then polyol glycidyl ether, an aqueous emulsion and a thickening agent are sequentially added and stirred for 10-15min to obtain a main agent part; adding the cross-linking agent into the main agent component before bonding the plywood, stirring for 3-5min, and uniformly dispersing to obtain the formaldehyde-free adhesive for the plywood.

Technical Field

The invention belongs to the technical field of macromolecules, and particularly relates to a formaldehyde-free adhesive for a plywood and a preparation method thereof.

Background

With the continuous improvement of the quality of life of people, some factors which are ignored by people before are more and more valued, wherein the pollution of indoor decoration is an extremely important aspect. The decoration pollution gas mainly comprises formaldehyde, benzene, toluene, ammonia and the like, wherein the formaldehyde is determined as carcinogenic and teratogenic substances by the world health organization. The formaldehyde is mainly from various indoor plywood sheets, and the formaldehyde released by the plywood sheets is mostly from formaldehyde adhesives in the plywood sheets. The formaldehyde adhesives, namely urea-formaldehyde resin, phenolic resin adhesive and melamine-urea-formaldehyde resin adhesive, are favored by plywood manufacturers due to excellent cohesiveness, manufacturability and high cost performance, and account for nearly 90% of the adhesive consumption in the plywood market.

At present, various adhesives for formaldehyde-free plywood are rapidly developed and continuously impact the market, and the formaldehyde-free adhesives are expected to be gradually replaced, so that a new hope is brought to the non-hydroformylation process of the industry, such as isocyanate non-formaldehyde adhesives, bio-based soybean adhesives and the like, and CN101524857A discloses a process for preparing the formaldehyde-free plywood by using isocyanate, wherein the process comprises a plurality of layers of single boards formed by combining adjacent layers in a cross structure or a parallel structure, a glue layer is arranged between the adjacent single boards, and the adhesive of the glue layer is isocyanate. The spray sizing method is adopted in the sizing procedure of the method, so that the sizing amount of the board is greatly reduced, the formaldehyde emission of the plywood is far lower than the relevant standard, however, the method directly uses pure pMDI as the curing agent, the reaction activity is high, the speed is high, the glue has short working life and high process requirement, and the quality stability of the product is influenced when the glue is applied to the plywood manufacturing and is slightly controlled badly. The bio-based soybean glue has poor stability, poor water resistance and higher mildew risk, the water resistance and mildew resistance are improved by some specific technologies in the related researches at present, but the obtained effect is limited, CN110982487A discloses a process for preparing aldehyde-free plywood by using aldehyde-free soybean protein adhesive with a multiple network structure, the bonding strength of the prepared 3-layer poplar plywood can only pass the requirement of II-type plywood, and the mildew resistance test is only observed for 15 days, so that the storage and use period of the adhesive which cannot meet the actual production requirement of a factory can be 3 months.

The method breaks through the industry tradition of 'no formaldehyde and no glue' in the plywood market, and the method is particularly urgent for preparing the formaldehyde-free adhesive for the plywood with excellent comprehensive performances such as cohesiveness, manufacturability, environmental friendliness and the like.

Disclosure of Invention

The purpose of the invention is as follows: aiming at the problems of the prior formaldehyde-free adhesive in the application of the adhesive in the plywood industry, such as: the invention provides a formaldehyde-free adhesive for plywood with excellent comprehensive performances such as cohesiveness, manufacturability, environmental protection and the like and a preparation method thereof, which are used in the plywood manufacturing industry.

The technical scheme is as follows: the invention provides a formaldehyde-free adhesive for plywood, which is divided into two components, namely a main agent and a cross-linking agent, wherein the main agent part of the product consists of the components except the cross-linking agent.

Specifically, the raw material formula of the formaldehyde-free adhesive for the plywood comprises the following components in parts by weight:

20-40 parts of water-based emulsion

50-100 parts of water

10-20 parts of polyol glycidyl ether

30-70 parts of filler

5-10 parts of thickening agent

0.1 to 0.5 portion of defoaming agent

0.2 to 0.5 portion of dispersant

6-40 parts of cross-linking agent

The aqueous emulsion is a product obtained by carrying out polymerization reaction on monomers and water at a certain temperature under the action of an emulsifier and an initiator, and comprises but is not limited to vinyl acetate-ethylene copolymer aqueous emulsion, polyvinyl acetate aqueous emulsion, acrylic polymer emulsion (including but not limited to vinyl acetate-ethylene copolymer aqueous emulsion, acrylic latex, organosilicon modified acrylic emulsion and the like), other rubber aqueous emulsion such as neoprene latex and the like, and all the emulsions are emulsions without benzene monomers such as styrene, methyl styrene and the like; further, the pH value of the emulsion of the invention is 4-8, more preferably 4-6; still further, the emulsions of the present invention have a Tg of between-20 ℃ and 25 ℃.

The polyhydric alcohol glycidyl ether is an oligomer with a main chain containing ether bonds (-R-O-R-), and an end group or a side group containing more than or equal to hydroxyl (-OH). It is prepared by ring-opening polymerization of low molecular weight polyol as initiator and olefin oxide under the action of catalyst. Such as glyceryl polyethers, polyoxypropylene diols and triols, polytetrahydrofuran diols, and the like.

Further, the present invention is preferably a glyceryl polyether, and further, the glyceryl polyether of the present invention is obtained by polymerizing glycerin and ethylene oxide, wherein different ethylene oxide is reacted with glycerin to obtain different products, the glyceryl polyether of the present invention preferably has 3 to 50, more preferably 7 to 31, and the glyceryl polyether having the ethylene oxide in the range of 7 to 31 may include, but is not limited to, glyceryl polyether-7, glyceryl polyether-8, glyceryl polyether-12, glyceryl polyether-15, glyceryl polyether-18, glyceryl polyether-20, glyceryl polyether-26, glyceryl polyether-31, etc. Further, the number of moles of ethylene oxide is preferably 12 to 18.

The fillers described herein include both inorganic and organic fillers. In the present invention, one or more of calcium carbonate, barium sulfate, white carbon black, clay, gypsum powder, talc powder, starch, flour, and wood powder are preferably mixed. Further, the inorganic filler of 800 mesh heavy calcium carbonate is preferable in the present invention.

The thickening agent comprises an inorganic thickening agent, a cellulose thickening agent, a polyacrylic acid thickening agent, a polyurethane thickening agent and the like. Further preferred are bentonite, attapulgite, montmorillonite, methyl cellulose, and carboxymethyl cellulose. Further, montmorillonite is preferred in the present invention.

The dispersants of the present invention include inorganic and organic dispersants. Further, the present invention preferably mixes one or more of water glass, sodium tripolyphosphate, sodium hexametaphosphate, sodium pyrophosphate, sodium polyacrylate, sodium lauryl sulfate, methylpentanol, and the like. Further, sodium polyacrylate salts are preferred in the present invention.

As the defoaming agent used in the aqueous coating product, a mineral oil type defoaming agent, a silicone type defoaming agent, a polyether type defoaming agent, a self-emulsifying defoaming agent and the like are generally used. However, the invention unexpectedly discovers that the use of polyether defoaming agent has better performance than the series defoaming agent, further, the preferable polyether defoaming agent has the molecular weight of more than or equal to 3000, hydroxyl functional groups of more than or equal to 3 and the solubility of more than or equal to 5g/L, and further, the preferable polyether GPE series defoaming agent is provided.

The cross-linking agent is aliphatic isocyanate, aromatic isocyanate and the like. Further, Toluene Diisocyanate (TDI), diphenylmethane diisocyanate (MDI), polymeric diphenylmethane diisocyanate (pMDI), isophorone diisocyanate (IPDI), Hexamethylene Diisocyanate (HDI), and the like are preferable in the present invention.

The invention also discloses a preparation method of the formaldehyde-free adhesive for the plywood, which comprises the following specific steps:

1. sequentially adding water, a dispersing agent and a defoaming agent into a disperser, stirring for 3-5min, then adding a filler, stirring for 15-20min, sequentially adding polyol glycidyl ether, an aqueous emulsion and a thickening agent, and stirring for 10-15min to obtain a main agent part;

2. adding the cross-linking agent into the main agent component before bonding the plywood, stirring for 3-5min, and uniformly dispersing to obtain the formaldehyde-free adhesive for the plywood.

In addition, the invention also discloses a preparation method of the plywood, which comprises the following specific steps:

1. gluing the veneer with formaldehyde-free adhesive in a working life by using veneer gluing equipment, wherein the single-side gluing amount is 160-flour-added 280g/m²；

2. And (3) carrying out veneer assembly on the glued veneers according to the odd layer principle and the fiber directions of the adjacent veneers are mutually vertical to obtain the veneer blank. Opening the slab, aging for 30-60min, and pre-pressing at 0.6-1.0MPa for 30-60 min;

3. and (3) hot-pressing the pre-pressed plate blank at the temperature of 110-.

Has the advantages that:

the formaldehyde-free adhesive product for the plywood disclosed by the invention has the advantages of no formaldehyde release, long working life and opening time and good cohesiveness, can be used for preparing the plywood under the condition of not changing the existing mature preparation production line and process in the plywood industry, does not release formaldehyde in the obtained plywood, and overcomes the defect that the performance, process, environmental friendliness and the like of the existing adhesive can not be considered when the adhesive is applied to the plywood industry.

Furthermore, the plywood prepared by the adhesive can pass a type I plywood dipping and stripping test, and the bonding strength is more than or equal to 1.0 Mpa;

furthermore, in order to meet the process requirements of plywood production, the working life of the adhesive is more than or equal to 60min, and the opening time is more than or equal to 60 min;

furthermore, all the raw materials of the invention are formaldehyde-free adhesives, and the formaldehyde-free adhesives belong to formaldehyde-free adhesives.

Detailed Description

In order to make the technical solutions of the present application better understood by those skilled in the art, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the embodiments of the present application, and it is obvious that the described embodiments are only some embodiments of the present application, but not all embodiments.

I test method

The pot life evaluation method comprises the following steps:

the adhesive is prepared, the viscosity of the adhesive is continuously tested by using a digital rotational viscometer at 25 ℃ under the condition of 60rpm of a 7# rotor, and the time T when the viscosity of the adhesive reaches 2 times of the initial test viscosity is recorded, namely the working life of the adhesive.

The evaluation method of the free formaldehyde emission of the adhesive comprises the following steps:

determination of 3.16 free formaldehyde content in GB/T14074-2017

The preparation method of the plywood of the embodiment of the invention comprises the following steps:

1. gluing the single board with formaldehyde-free adhesive in the use period with single board gluing equipment to obtain single board glue with single glue spreading amount of 180g/m²；

2. And (3) carrying out veneer assembly on the glued veneers according to the odd layer principle and the fiber directions of the adjacent veneers are mutually vertical to obtain the veneer blank. Opening the plate blank, aging for 60min, and pre-pressing at 0.8MPa for 30 min;

3. and (3) carrying out hot pressing on the pre-pressed plate blank, wherein the hot pressing temperature is 120 ℃, the hot pressing time is 1min/mm calculated according to the thickness of the plate blank, and the hot pressing pressure is 0.8Mpa, so that the plywood product is obtained.

Method for evaluating open storage time:

1. preparing the adhesive;

2. gluing the veneers for assembly to obtain an assembled plywood;

3. sequentially pre-pressing the assembled plywood to obtain a pre-pressed board;

4. carrying out hot pressing and curing on the pre-pressed board to obtain a plywood sample board, and sawing the sample board to carry out dipping stripping and bonding strength test;

5. calculating the open display time: timing is carried out from the start of gluing the veneers to the end of prepressing the assembled veneers, meanwhile, the plywood sample plate passes the I-type dipping and stripping test, the gluing strength is more than or equal to 1.0Mpa, and the time is the opening and standing time.

The evaluation method of formaldehyde emission of the plywood comprises the following steps:

method for measuring 4.60 formaldehyde emission in GB/T17657-2013-1 m3 climate box

Adhesive adhesion evaluation method:

4.19.4 class I dip-stripping test in GB/T17657-2013

4.17 bond Strength determination in GB/T17657-2013, wherein specimen treatment is carried out as prescribed in GB/T17657-2013 at 4.17.5.2.3

II raw material

Example III

The formaldehyde-free adhesive for the plywood is prepared from the following components in parts by weight according to the preparation method:

IV results

The adhesive product prepared in the above example and 7-layer eucalyptus plywood with 2.2mm thickness of veneer prepared by the plywood preparation process by using the adhesive have the following detection results by the evaluation method:

note: the impregnation peel test example was not passed, and the adhesion strength was recorded as "0".

The adhesive and the plywood prepared by the adhesive disclosed by the invention have no formaldehyde detected, and the environmental protection performance is greatly improved compared with that of the traditional formaldehyde adhesive.

From the results of 9 groups of examples, i.e., examples 1 to 6, comparative examples 1, 2, 7, etc., it is understood that the adhesives prepared using the vinyl acetate-ethylene copolymer aqueous emulsion, the acrylic polymer emulsion, and the neoprene emulsion as the aqueous emulsion have a long pot life of more than 60min, the open-time aging time of more than 60min when the plywood is prepared using the adhesives, the plywood samples prepared using the adhesives can pass the I-type board dip-peel test, and the bonding strength is more than 1.0Mpa, while the adhesives prepared using the styrene-butadiene latex containing the benzene monomer and the styrene-acrylic emulsion and the adhesives prepared using the adhesives for preparing the plywood samples do not have the desired effects in terms of bonding performance and process.

From the results of 5 groups of examples 1 to 3, 8 and 9, it can be seen that even when the aqueous emulsion does not contain the benzene-based monomer, the adhesive prepared has a Tg too high (> 25 ℃) or too low (< 25 ℃), which makes the adhesive performance not pass the detection requirements.

From the results of the 4 groups of examples 1 to 3, comparative example 10 and the like, it can be seen that when the pH of the aqueous emulsion is too high (> 8), the pot life of the prepared adhesive is only 15min, and the bonding performance can not pass the detection requirement.

From the results of 3 groups of examples, namely example 1, comparative example 3, comparative example 4 and the like, it can be seen that the effect of adopting the defoaming agent GPE3000 is better than that of the defoaming agent NOPCO NXZ, the defoaming agent NOPCO NXZ is better than that of not adding the defoaming agent, the main influence is reflected on the bonding strength of the prepared plywood sample plate, and meanwhile, the opening aging time when the plywood sample plate is prepared is influenced to a certain extent.

From the results of 4 groups of examples, namely example 2, example 5, comparative example 6 and the like, it can be seen that the addition of the glyceryl polyether G-12 can significantly improve the open-time of the plywood sample when the plywood sample is prepared.

The above description is only a preferred embodiment of the present application and is not intended to limit the present application.