阅读说明：本技术 一种专用于人造板的水性无甲醛胶粘剂及制备方法 (Aqueous formaldehyde-free adhesive special for artificial board and preparation method thereof ) 是由 朱玉国 李炳泉 赵康 董春生 唐立超 于 2021-07-16 设计创作，主要内容包括：本发明公开了一种专用于人造板的水性无甲醛胶粘剂及其制备方法,所述的无甲醛胶粘剂至少含有一种水性胶粘剂乳液,并且该水性无甲醛胶粘剂乳液经过添加破乳剂进行破乳处理后得到。所述的水性胶粘剂乳液为丙烯酸类水性乳液,按共聚单体的总量100％含量计,含有1-10％的亲水性单体组分。本发明所述的产品,其所用的原料为水性无甲醛胶粘剂,甲醛零释放,初粘力高,滚涂、施工方便,并且具有粘接强度高、耐水性能优越等优点。(The invention discloses a special aqueous formaldehyde-free adhesive for artificial boards and a preparation method thereof. The aqueous adhesive emulsion is acrylic aqueous emulsion and contains 1-10% of hydrophilic monomer component according to 100% of total content of comonomer. The product of the invention uses the water-based formaldehyde-free adhesive as the raw material, has zero formaldehyde release, high initial adhesion, convenient roll coating and construction, and has the advantages of high bonding strength, excellent water resistance and the like.)

1. The aqueous formaldehyde-free adhesive special for the artificial board is characterized by at least comprising an aqueous adhesive emulsion, and the aqueous formaldehyde-free adhesive emulsion is obtained by adding a demulsifier to perform demulsification treatment.

2. The aqueous formaldehyde-free adhesive for artificial boards according to claim 1, wherein the aqueous adhesive emulsion comprises: polyvinyl acetate aqueous emulsion, polyethylene-vinyl acetate aqueous emulsion, acrylic aqueous emulsion, polyurethane aqueous emulsion, epoxy aqueous emulsion, silicone aqueous emulsion, and rubber aqueous adhesive emulsion.

3. The aqueous formaldehyde-free adhesive special for artificial boards according to claim 2, wherein the aqueous adhesive emulsion is an acrylic aqueous emulsion containing 1-10% of hydrophilic monomer component based on 100% of total comonomer content; the hydrophilic monomer is one or more selected from acrylic acid, methacrylic acid or hydroxyethyl acrylate and hydroxypropyl acrylate.

4. The aqueous formaldehyde-free adhesive special for artificial boards as claimed in claim 1, wherein the glass transition temperature of the aqueous adhesive emulsion is-50 ℃ to 15 ℃, and the Brookfield viscosity of the mixed liquid of the aqueous adhesive is 8000-20000 cP.

5. The aqueous formaldehyde-free adhesive special for artificial boards according to claim 1, wherein the demulsification treatment comprises: and mixing the adhesive emulsion with a demulsifier, and carrying out high-speed shearing.

6. The aqueous formaldehyde-free adhesive special for artificial boards according to claim 1, wherein the adhesive further comprises a dispersant, a defoamer, a filler, a film forming aid, a bactericide, a thickener, a pH regulator, a coupling agent and a curing agent.

7. The method for preparing the aqueous formaldehyde-free adhesive according to claim 1, which comprises the steps of: adding a dispersing agent, a bactericide, a pH regulator, a defoaming agent and a proper amount of water into a mixing kettle, then slowly adding a filler, uniformly mixing, further adding the aqueous formaldehyde-free emulsion, adding a thickening agent after the addition is finished, and adjusting to a proper viscosity to obtain a mixed feed liquid; after the mixed material liquid is prepared, a demulsifier can be further slowly added into the mixed material liquid step by step according to the requirement of the use amount, and the high-speed shearing is carried out at the same time, and a curing agent can be further added according to the requirement, so that the waterborne formaldehyde-free adhesive is obtained.

8. The method for preparing the aqueous formaldehyde-free adhesive according to claim 7, wherein the demulsifier is an organic acid or organic salt demulsifier; the dosage of the demulsifier is 1-10 parts based on 100 parts of the total amount.

9. The method for preparing the water-based formaldehyde-free adhesive according to claim 7, wherein the filler is one or more of kaolin, attapulgite, quartz powder, talcum powder, titanium dioxide, ZnO, heavy calcium, light calcium, wollastonite, barium sulfate and mica powder.

10. The method for preparing the water-based formaldehyde-free adhesive according to claim 7, wherein the curing agent is one or more selected from epoxy resin, amine curing agent for epoxy resin and isocyanate curing agent.

Technical Field

The invention belongs to the field of high molecular polymers, and particularly relates to a special aqueous formaldehyde-free adhesive for artificial boards and a preparation method thereof.

Background

For many years, the artificial board industry has used a large amount of urea-formaldehyde resin, phenol-formaldehyde resin glue and melamine-formaldehyde resin glue and is called three major glues for the artificial board industry, namely three-aldehyde glue, however, the three-aldehyde glue contains formaldehyde and is harmful to human bodies and the environment, so the environmental protection performance of artificial board products becomes a hotspot of research in recent years, and a novel formaldehyde-free environment-friendly adhesive is urgently needed to be developed to meet the market demand.

At present, the water-based polyacrylic resin emulsion is used as a main raw material to replace a formaldehyde adhesive, and becomes a research hotspot, wherein CN107245308A discloses an application method of a styrene/acrylic acid adhesive for bonding artificial boards. The application method comprises the step of uniformly mixing styrene acrylic acid and the batter according to a certain proportion to form the two-component adhesive for use. The styrene/acrylic latex is used as a main adhesive component, the batter is a filler and a secondary adhesive component, the adhesive penetration probability of the ethylene/acrylic latex in the sizing process can be effectively reduced, and the styrene/acrylic latex adhesive is greatly helpful for improving the overall viscosity of the adhesive and reducing the production cost.

However, the improvement of the viscosity is not equal to the improvement of the initial adhesion, and in the actual use process, the initial adhesion of the adhesive using the aqueous polyacrylic resin emulsion is far lower than that of the phenolic resin adhesive, which causes the problems of easy slipping, unstable glue coating control and the like in the gluing process of production, and directly influences the product quality. Therefore, there is an urgent need to develop a formaldehyde-free adhesive with high initial adhesion for artificial boards and a preparation method thereof, which are used for improving production efficiency and stabilizing product quality.

Disclosure of Invention

The purpose of the invention is as follows: aiming at the defects in the prior art, the invention aims to provide the aqueous formaldehyde-free adhesive special for the artificial board and the preparation method thereof.

The high initial adhesion water-based formaldehyde-free adhesive specially used for the artificial board at least comprises a water-based formaldehyde-free adhesive emulsion, and the water-based formaldehyde-free adhesive emulsion is obtained by adding a demulsifier to perform demulsification treatment.

The aqueous formaldehyde-free adhesive emulsion is an aqueous emulsion product produced by an emulsion polymerization process, and can also be an aqueous formaldehyde-free adhesive emulsion obtained by high-speed shearing and dispersing. The formaldehyde-free in the invention means that formaldehyde is not added and used as a raw material or an auxiliary agent in the raw materials.

The preferable aqueous formaldehyde-free adhesive emulsion of the invention preferably uses an acrylic aqueous emulsion, and further, the acrylic aqueous emulsion of the invention contains 1-10% of hydrophilic monomer component based on 100% of the total content of the comonomer, and further, the hydrophilic monomer is selected from one or more of acrylic acid, methacrylic acid or hydroxyethyl acrylate and hydroxypropyl acrylate.

Furthermore, the glass transition temperature (Tg) of the aqueous formaldehyde-free adhesive emulsion is preferably-50 ℃ to-15 ℃, and more preferably-30 ℃ to-5 ℃.

The demulsification is a method for breaking a protective layer formed by an emulsifier on the surface of emulsion particles in an emulsion by treating a stable emulsion by a physical method or a chemical method.

The physical demulsification method provided by the invention can be divided into a gravity demulsification method, a centrifugal demulsification method, an electrical demulsification method, a membrane wetting coalescence demulsification method, a grinding demulsification method, a high-voltage static demulsification method, a violent stirring demulsification method, a vibration demulsification method, a high-speed centrifugal demulsification method, a heating demulsification method, a freezing demulsification method and the like.

The chemical demulsification is obtained by adding 0.01-30 parts of demulsifier into the aqueous formaldehyde-free adhesive emulsion by 100 parts of the total amount, uniformly mixing and stirring to uniformly demulsify the aqueous formaldehyde-free adhesive emulsion, wherein the preferable dosage of the demulsifier is 1-10 parts. Wherein the aqueous formaldehyde-free adhesive emulsion and the demulsifier are both calculated according to 100 percent of solid content.

The demulsifier comprises an organic demulsifier or an inorganic demulsifier, and the like, wherein the organic demulsifier comprises an organic acid, an organic base, an organic salt, a cationic organic demulsifier, an alcohol product, and the like; organic acids include, but are not limited to, acetic acid, acrylic acid, polyacrylic acid, methacrylic acid, polymethacrylic acid, citric acid, and the like; organic salts include, but are not limited to, acrylates, acetates, polyacrylates, maleates, polymaleates, and the like; cationic organic demulsifiers include, but are not limited to, polyacrylamide grafts and copolymers, epichlorohydrin reactants, quaternary ammonium salts, imine products such as polyethyleneimine, and the like. Alcohol products can use various monohydric, dihydric, and polyhydric alcohols having C atoms of greater than or equal to three, such as C1-C18, including but not limited to methanol, ethanol, propanol, butanol, glycerol, and the like.

Inorganic demulsifiers including products such as inorganic acids including but not limited to hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, etc., inorganic bases including sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide, etc., and inorganic salts including but not limited to sodium salts such as sodium chloride, sodium sulfate, sodium carbonate, sodium nitrate, etc., as common examples; potassium salts, such as potassium chloride, potassium sulfate, potassium carbonate, potassium nitrate and the like; magnesium salts, such as magnesium chloride, magnesium sulfate, magnesium carbonate, magnesium nitrate, etc.; common examples of the calcium salt include calcium chloride, calcium sulfate, calcium nitrate, etc.; as the aluminum salt, there may be mentioned common examples such as aluminum chloride, aluminum sulfate, aluminum nitrate and the like.

The demulsifier of the present invention may be selected from one or more of organic demulsifiers, inorganic demulsifiers, and other demulsifiers, and further, the preferred organic demulsifier of the present invention is selected from organic acid demulsifiers and organic salt demulsifiers, and further, preferably from polyacrylic acid demulsifiers.

Furthermore, in order to improve the performance of the product and reduce the cost, products such as a dispersing agent, a defoaming agent, a filler, a film forming aid, a bactericide, a thickening agent, a pH regulator, a coupling agent, a curing agent and the like can be added into the emulsion.

The dispersant of the invention is a universal dispersant which can be used in aqueous systems, and the dosage of the dispersant is 0-5 parts, preferably 0.1-2 parts based on 100 parts of aqueous formaldehyde-free adhesive emulsion and 100 percent of solid content of the emulsion.

The defoaming agent of the invention refers to a defoaming agent which can be used in a water-based system, and the dosage of the defoaming agent is 0-2 parts, preferably 0.1-1 part based on 100% of water-based formaldehyde-free adhesive emulsion and the emulsion is calculated by 100% of solid content.

The filler of the invention can be selected from inorganic and organic fillers, and the inorganic filler can include but is not limited to kaolin, attapulgite, quartz powder, talcum powder, titanium dioxide, ZnO, heavy calcium, light calcium, wollastonite, barium sulfate, mica powder and the like; the organic filler comprises one or more of flour, wood flour, glutinous rice flour, lignin and the like, and the mesh number of the inorganic filler is preferably 400-2000 meshes, and is preferably 800-1250 meshes. The filler of the invention is added in an amount of 0-150 parts, preferably 20-120 parts, more preferably 30-100 parts based on 100% of solid content of the aqueous formaldehyde-free adhesive emulsion.

The thickening agent of the invention can be ASE thickening agent, polyurethane thickening agent, HASE thickening agent or cellulose ether thickening agent, and the addition amount of the thickening agent is 0-10 parts, preferably 0.1-5 parts, and more preferably 0.5-3 parts based on 100 parts of aqueous formaldehyde-free adhesive emulsion and 100% of solid content of the emulsion.

The coupling agent of the present invention refers to a coupling agent that can be used in aqueous systems, including but not limited to silane coupling agents, phthalate ester coupling agents, etc., and is used in an amount of 0-5 parts, preferably 0.5-3 parts, based on 100 parts of aqueous formaldehyde-free adhesive emulsion and 100% of solid content of the emulsion.

Further, the aqueous formaldehyde-free adhesive emulsion is a mixed liquid obtained by adding a proper amount of water, a dispersing agent, a bactericide, a filler, a pH regulator, a defoaming agent, a thickener, a coupling agent and other additives, and is uniformly called as a mixed material liquid (at this time, a demulsifier is not added to the mixed material liquid or the emulsion in the mixed material liquid is not demulsified yet), the Brookfield viscosity range of the mixed material liquid can be 1000-1000000 cP, preferably 5000-50000 cP, and further preferably 8000-20000cP, and the viscosity test condition of the aqueous formaldehyde-free adhesive emulsion is data obtained by using a Brookfield series viscometer and testing at 25 ℃ at a rotating speed of 30 rpm.

The curing agent is selected from epoxy resin, amine curing agents for epoxy resin and isocyanate curing agents. Further, the epoxy resin is preferably a water-based epoxy resin, and the amine curing agent for epoxy resin is preferably an epoxy resin which can be emulsified or dissolved in water, including but not limited to emulsified DER 331 water-based epoxy, hydantoin epoxy, water-soluble epoxy; the amine curing agent for the epoxy resin comprises one or more of polyamide, isophorone diamine, cyclohexane diamine, methyl cyclopentyl diamine, 4, 4-diaminodicyclohexyl methane polyoxypropylene diamine, polyoxypropylene triamine or polyoxyethylene diamine and 3- [ (6-amino-2, 4, 4-trimethylhexyl) amino ] propionitrile, wherein the molecular weight of a structural unit segment of polyoxypropylene or polyoxyethylene is between 200 and 5000. The isocyanate curing agent includes, but is not limited to, Toluene Diisocyanate (TDI), isophorone diisocyanate (IPDI), diphenylmethane diisocyanate (MDI), polymeric diphenylmethane diisocyanate (pMDI), dicyclohexylmethane diisocyanate (HMDI), Hexamethylene Diisocyanate (HDI), Lysine Diisocyanate (LDI), and the like. The curing agent of the invention is added in an amount of 0-30 parts, preferably 5-20 parts, more preferably 7-15 parts based on 100% of the solid content of the aqueous formaldehyde-free adhesive emulsion.

Typically, in a preferred embodiment of the present invention, the aqueous formaldehyde-free adhesive is obtained by adding 1-10 parts of an organic demulsifier to 100 parts of the total amount of an acrylic aqueous emulsion, mixing and stirring uniformly to allow the aqueous formaldehyde-free adhesive emulsion to be demulsified uniformly, wherein the aqueous formaldehyde-free adhesive emulsion and the demulsifier are both based on 100% of solid content. And the emulsion also contains water, a dispersing agent, a defoaming agent, a bactericide, a pH regulator, a filler, a thickening agent, a coupling agent, a curing agent and other auxiliaries, so that the Brookfield viscosity range of the emulsion mixed material liquid is 8000-20000cP, the emulsion contains 1-10% of hydrophilic monomer components, the glass transition temperature of the emulsion is-30-5 ℃, the filler is 30-100 parts, and the curing agent is 7-15 parts.

Further, the invention also provides a preparation method of the aqueous formaldehyde-free adhesive, which comprises the following steps:

adding a proper amount of water, a dispersing agent, a defoaming agent, a bactericide, a pH regulator and a coupling agent into a mixing kettle, then slowly adding a filler, uniformly mixing, further adding other auxiliaries and the aqueous formaldehyde-free emulsion, adding a thickening agent after the addition is finished, and regulating to a proper viscosity to obtain a mixed feed liquid; after the mixed material liquid is prepared, a demulsifier can be further slowly and gradually added into the mixed material liquid according to the requirement of the use amount, and high-speed shearing is carried out, the stirring speed is preferably higher than 100rpm, the stirring blade is preferably a dispersion plate stirring blade, the stirring time is longer than 20min, and a curing agent can be further added according to the requirement, so that the high initial adhesion waterborne formaldehyde-free adhesive is obtained.

The adhesive obtained by the preparation method can be coated in a solid wood composite veneer by using a roller coating method or other methods, and then is further assembled, cold-pressed and hot-pressed to obtain the plywood, wherein the process for preparing the plywood is a common process for the solid wood composite floor, for example, the common cold-pressing condition is that the cold-pressing time is 30-90min, and the cold-pressing pressure is 0.6-2 Mpa; the hot pressing process conditions are as follows: wherein the hot pressing temperature is 90-130 ℃, the pressure is 0.6-2Mpa, and the hot pressing speed is 50-80mm of plate thickness per minute. After 24 hours of curing, the hot-pressed plate is further tested according to GB/T17657-2013.

Has the advantages that:

the artificial board adhesive system is different from the traditional trialdehyde resin, the raw material used by the artificial board adhesive system is a water-based formaldehyde-free adhesive, formaldehyde is zero released, the initial adhesion is high, roll coating and construction are convenient, and the artificial board adhesive system has the advantages of high adhesive strength, excellent water resistance and the like.

In addition, the invention also breaks through the concept that emulsion breaking cannot be realized in the emulsion system adhesive for a long time. For example, emulsions used in the artificial board industry are used in formulations by directly using emulsion products with other additives added thereto, and generally cannot be used if the emulsion breaking of the products means that the formulations of the products fail. The researchers of the invention unexpectedly find that the product obtained by the demulsification method can be kept stable without demulsification and the dipping stripping performance of the adhesive is not influenced.

In order to achieve the effect, the Tg range of the emulsion, the viscosity of the emulsion mixed material liquid and whether the emulsion contains hydrophilic monomers or not need to be properly controlled, and furthermore, the Brookfield viscosity range of the emulsion mixed material liquid is preferably 8000-20000cP, the emulsion contains 1-10% of hydrophilic monomer components, the glass transition temperature of the emulsion is-30-5 ℃, under the condition, not only the dipping and stripping performance is not influenced, but also the initial viscosity is unexpectedly improved.

The specific implementation mode is as follows:

the invention is further illustrated by the following specific examples, and table 1 below is the basic information on the raw materials required for use in the examples of the invention.

TABLE 1 specification designations and basic Properties of the different emulsions

TABLE 2 Specification designations and basic Properties of the other raw materials

Description of the test corresponding standard methods:

1. the initial viscosity is detected and tested by referring to GB/T4852 rolling ball method which is a pressure sensitive adhesive tape initial viscosity test methodAngle, 20 ℃ unified, wire bar device to about 200g/m unified²Coating the coating amount on a wire board, quickly performing initial viscosity test, testing each formula batch for 5 times, and then averaging;

2. the dipping and peeling performance is tested according to a method 4.19.4.1-a of GB/T17657-2013 physicochemical property test method for artificial boards and decorative artificial boards, and the basic test method is as follows:

soaking the test piece in boiling water for 4 hours, taking out the test piece, and drying the test piece in a drying box at the temperature of 63 +/-3 ℃ for 20 hours; soaking the test pieces in boiling water for 4 hours, taking out the test pieces, drying the test pieces in a drying oven at the temperature of (63 +/-3) DEG C for 3 hours, and observing whether the adhesive layer is stripped and the stripping degree of the adhesive layer, wherein the stripping length of each side of the same adhesive layer of each test piece is required to be accumulated to be not more than 1/3 of the length of the adhesive layer, the test piece is judged to pass the soaking stripping when not more than 1/3, and the test piece is judged to not pass the soaking stripping when not more than 1/3;

3. and (3) testing the gluing stability of the glue rolling machine, directly using a four-roller coating gluing machine for the plywood to carry out gluing test after glue preparation is finished, and observing the gluing uniformity of the glue and whether the board slips or is too slow in the gluing process. The single-side gluing amount is controlled to be 220 +/-20 g/m²。

The preparation methods in the examples are as follows:

adding 40 parts of water into a mixing kettle, then adding 1 part of dispersing agent, a proper amount of bactericide, a pH regulator and a defoaming agent, stirring uniformly, then slowly adding 50 parts of filler (heavy calcium), further pulping, completing the pulping within about 10-40 minutes, further adding 100 parts of emulsion after mixing uniformly, after the addition is completed, further adding a proper amount of water, controlling the theoretical solid content of the adhesive to be 50 +/-2%, then further adding a thickening agent, and regulating the viscosity to 10000 +/-1000 cP (Brookfield viscometer, 30rpm, 25 ℃), thus obtaining mixed feed liquid; after the mixed material liquid is prepared, a demulsifier can be further slowly and gradually added into the mixed material liquid according to the actual condition requirement, and high-speed shearing is carried out, the stirring speed is preferably more than or equal to 100rpm, the stirring blade is preferably a dispersion plate stirring blade, the stirring time is more than or equal to 20min, and a curing agent can be further added according to the requirement, so that the high initial viscosity aqueous formaldehyde-free adhesive is obtained.

The formulations of examples 1-3 and comparative examples 1-3 are shown in Table 3 below.

TABLE 3 initial tack and stability after demulsification of Adhesives formulated with different emulsions

From the results, the emulsion is not enough in initial viscosity without using the emulsion breaker, and the product is easy to slip in the using process; after the demulsifier is used, if the emulsion does not contain hydrophilic monomers and the Tg of the emulsion is not in the range of-50 to 15 ℃, the emulsion is easy to generate the phenomena of instability, agglomeration and the like, so that the product cannot be normally used.

Further, on the basis of example 1, the viscosity of the adhesive is controlled by controlling the addition amount of the thickening agent, so that the influence of the adhesive with different viscosity on the initial viscosity and the gluing stability of the adhesive after demulsification is examined.

TABLE 4 Effect of Adhesives of different viscosities on initial tack and gumming stability after demulsification

	Viscosity, cP	Initial tack	Rubber coating stability test of roller rubber machine
				Example 1	10000	2# ball, 12mm	Is normal
Comparative examples 1 to 4	50000	2# ball, 27mm	Poor fluidity and uneven gluing
				Comparative examples 1 to 5	2000	Fail to test	Gel delamination after 10min of glue
Comparative examples 1 to 6	500	Fail to test	Gel delamination after 10min of glue

Still further, on the basis of the examples and the above comparative examples 1 to 3, 7 × 2.2mm plywood was prepared by adding 10% of curing agent and mixing, and then the impregnation peeling test was performed after the hot pressing of 0.8Mpa, 30min of cold pressing pressure, 120 ℃ of hot pressing temperature, 0.8Mpa and 16min of hot pressing time, and the test results are shown in table 5:

table 5 dip strip results for different formulations

From the results, it can be seen that the initial viscosity of the product is poor without using a demulsifier, the product is easy to slip in the using process, and in addition, the viscosity of the adhesive is increased by adding a thickener, so that the initial viscosity can be increased to a certain extent, but the initial viscosity is not equal to the viscosity, so that the excessive increase of the viscosity causes poor fluidity of the adhesive, the gluing is not uniform, the actual application of the product is difficult to meet, and the dipping and stripping result of the plywood can also be reflected to a certain extent.