Polymer Latex for Wood Adhesives

Abstract

The present invention relates to a polymer latex for use in adhesive compositions, and to a method for preparing and using the polymer latex.More particularly, but not exclusively, the present invention relates to an aqueous adhesive composition comprising such a polymer latex, and to a method for preparing such an aqueous adhesive composition.

Description

[Technical field]

[0001] The present invention relates to a polymer latex for use in adhesive compositions, and to a method for preparing and using the polymer latex.More particularly, but not exclusively, the present invention relates to an aqueous adhesive composition comprising such a polymer latex, and to a method for preparing such an aqueous adhesive composition. [Background technology]

[0002] D4 wood adhesives require a certain durability because they are used in interior areas that are frequently exposed to running or condensing water for long periods of time and / or in exterior areas that are exposed to weather. A suitable adhesive not only has excellent dry adhesion performance, but also has excellent secondary performance such as water-resistant adhesion, boiling water-resistant adhesion and heat-resistant adhesion. Conventional water-based polymeric isocyanate adhesives are inadequate in terms of water-resistant adhesion, especially boiling water-resistant adhesion, but are good in terms of dry adhesion. Another challenge is harsher environments than conventional environments, such as high temperatures or high humidity for long periods of time.

[0003] In addition to the requirement of adhesion, extended stability (pot life) of the adhesive itself after the isocyanate compound is blended is desirable.

[0004] EP 1 754 766 A1 relates to an aqueous polymer dispersion for isocyanate crosslinking adhesives, comprising a polymer (1) obtained by emulsion polymerization of a monomer composition comprising at least one monomer selected from the group consisting of aromatic vinyl monomers and (meth)acrylate monomers, a crosslinkable monomer, and a different monomer, and a polymer (2) obtained by emulsion polymerization of a monomer composition comprising at least one monomer selected from the group consisting of aromatic vinyl monomers and (meth)acrylate monomers, a hydroxyl group-containing vinyl monomer, an ethylenically unsaturated carboxylic acid monomer, and a different monomer, wherein the polymers (1) and (2) have a Tg difference of 20 to 80°C.

[0005] It is an object of the present invention to provide a polymer latex for use in adhesive compositions which provides a long pot life after mixing with a hardener component, and which provides high wood bond strength suitable for use in wood adhesives, particularly D4 wood adhesives. Summary of the Invention

[0006] The following section summarizes certain aspects of the present invention.

[0007] According to a first aspect, the invention relates to a polymer latex for an adhesive composition, obtainable by free-radical emulsion polymerization of a mixture of ethylenically unsaturated monomers, The mixture of ethylenically unsaturated monomers may be (a) vinyl aromatic monomers, (b) a conjugated diene monomer, and (c) containing ethylenically unsaturated monomers having acid and / or hydroxyl functionality; The weight ratio of vinyl aromatic monomer (a) to conjugated diene monomer (b) ranges from 1.60 to 2.30, and the polymer latex has a median particle size of at least 220 nm.

[0008] The sum of the vinyl aromatic monomer (a) and the conjugated diene monomer (b) may range from 85.0 to 99.0% by weight, preferably from 90.0 to 98.0% by weight, based on the total weight of the monomers in the monomer mixture.

[0009] The mixture of ethylenically unsaturated monomers may be (a) The monomer mixture may contain 40 to 80% by weight, preferably 50 to 75% by weight, and more preferably 55 to 70% by weight, of a vinyl aromatic monomer, based on the total weight of the monomers in the monomer mixture.

[0010] The vinyl aromatic monomer (a) may be selected from styrene, alpha-methylstyrene, vinyltoluene, and combinations thereof. The vinyl aromatic monomer (a) may be selected from styrene.

[0011] The mixture of ethylenically unsaturated monomers may be (b) The monomer mixture may contain 15 to 50% by weight, preferably 20 to 45% by weight, and more preferably 25 to 40% by weight of a conjugated diene monomer, based on the total weight of the monomers in the monomer mixture.

[0012] Conjugated diene monomers (b) are 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, 2,4-hexadiene, 1,3-octadiene, 2-methyl-1,3-pentadiene, 2,3-dimethyl-1,3-pentadiene, 3,4-dimethyl-1,3-hexadiene, 2,3-diethyl-1,3-butadiene, 4,5-diethyl-1,3-octadiene, 3-butyl-1,3-octadiene, 3,7-dimethyl-1,3,6-octatriene, 2-methyl-6-methylene-1,7-octadiene, 7-methyl-3-methylene-1, The conjugated diene monomer (b) may be selected from 6-octadiene, 1,3,7-octatriene, 2-ethyl-1,3-butadiene, 2-amyl-1,3-butadiene, 3,7-dimethyl-1,3,7-octatriene, 3,7-dimethyl-1,3,6-octatriene, 3,7,11-trimethyl-1,3,6,10-dodecatetraene, 7,11-dimethyl-3-methylene-1,6,10-dodecatriene, 2,6-dimethyl-2,4,6-octatriene, 2-phenyl-1,3-butadiene, 2-methyl-3-isopropyl-1,3-butadiene, 1,3-cyclohexadiene, myrcene, ocimene, farnesene, and combinations thereof. The conjugated diene monomer (b) may be selected from 1,3-butadiene, isoprene, and combinations thereof. The conjugated diene monomer (b) may be selected from 1,3-butadiene.

[0013] The mixture of ethylenically unsaturated monomers may be (c) The monomer mixture may contain 0.2 to 6.0% by weight, preferably 0.3 to 5.0% by weight, more preferably 0.5 to 4.0% by weight, of an ethylenically unsaturated monomer having an acid functionality and / or a hydroxyl functionality, based on the total weight of the monomers in the monomer mixture.

[0014] The ethylenically unsaturated monomer (c) having an acid functional group can be selected from ethylenically unsaturated carboxylic acid monomers, ethylenically unsaturated sulfonic acid monomers, and ethylenically unsaturated phosphorus-containing acid monomers.The ethylenically unsaturated monomer (c) having an acid functional group can be selected from (meth)acrylic acid, crotonic acid, fumaric acid, itaconic acid, maleic acid, maleic anhydride, vinyl acetic acid, vinyl lactic acid, vinyl sulfonic acid, styrene sulfonic acid, 2-carboxyethyl (meth)acrylate, phenyl vinyl sulfonate, sodium 4-vinylbenzene sulfonate, 2-methyl-2-propene-1-sulfonic acid, 2-propene-1-sulfonic acid, 4-styrene sulfonic acid, 2-acrylamido-2-methyl-1-propane sulfonic acid, vinyl phosphonic acid, dimethyl vinyl phosphonate, diethyl vinyl phosphonate, diethyl allyl phosphonate, allyl phosphonic acid, and combinations thereof. The ethylenically unsaturated monomer having an acid functionality (c) may be selected from (meth)acrylic acid, itaconic acid, and combinations thereof.

[0015] The ethylenically unsaturated monomer (c) having a hydroxyl functional group can be selected from allyl alcohol, vinyl alcohol, N-methylol (meth)acrylamide, 1-penten-3-ol, hydroxyalkyl esters of ethylenically unsaturated acids, such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate and hydroxyethyl caprolactone acrylate, and combinations thereof. The ethylenically unsaturated monomer (c) having a hydroxyl functional group can be selected from hydroxyalkyl esters of ethylenically unsaturated acids, such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate and hydroxyethyl caprolactone acrylate. The ethylenically unsaturated monomer (c) having a hydroxyl functional group can be selected from hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl methacrylate, and combinations thereof.

[0016] The ethylenically unsaturated monomer (c) having an acid function and a hydroxy function may be selected from 3-allyloxy-2-hydroxy-1-propanesulfonic acid.

[0017] The weight ratio of vinyl aromatic monomer (a) to conjugated diene monomer (b) may range from 1.70 to 2.10.

[0018] The polymer latex may have a median particle size of at least 230 nm, preferably at least 250 nm.

[0019] The mixture of ethylenically unsaturated monomers may contain from 0.05 to 3.0 weight percent, preferably from 0.10 to 2.0 weight percent, and more preferably from 0.15 to 1.5 weight percent of the chain transfer agent, where the weight percentage is based on the total amount of monomers in the monomer mixture.

[0020] The chain transfer agent may be selected from n-dodecyl mercaptan, carbon tetrachloride, carbon tetrabromide, bromotrichloromethane, 4-methylbenzenethiol, isooctyl 3-mercaptopropionate, tert-nonyl mercaptan, 4,4'-thiobisbenzenethiol, tert-dodecyl mercaptan, α-methylstyrene dimer, thioglycolic acid, 2-ethylhexyl thioglycolate, butyl 3-mercaptopropionate, 1,8-dimercapto-3,6-dioxaoctane and combinations thereof, preferably tert-dodecyl mercaptan.

[0021] The mixture of ethylenically unsaturated monomers may further comprise (d) 0 to 20 weight percent of an ethylenically unsaturated monomer different from (a) to (c), based on the total weight of the monomers in the monomer mixture; The ethylenically unsaturated monomer different from (a) to (c) is preferably (d1) an ethylenically unsaturated nitrile compound, preferably selected from (meth)acrylonitrile, alpha-cyanoethyl acrylonitrile, fumaronitrile, alpha-chloronitrile, and combinations thereof; (d2) alkyl esters of ethylenically unsaturated acids, preferably selected from methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and combinations thereof; (d3) ethylenically unsaturated compounds having a primary or secondary amino group, preferably selected from (meth)acrylamide, 2-aminoethyl (meth)acrylate hydrochloride, 2-aminoethyl (meth)acrylamide hydrochloride, N-ethyl (meth)acrylamide, N-(3-aminopropyl) (meth)acrylamide hydrochloride, N-hydroxyethyl (meth)acrylamide, N-3-(dimethylamino)propyl (meth)acrylamide, [3-(methacryloylamino)propyl]trimethylammonium, N-[tris(hydroxymethyl)methyl] (meth)acrylamide, N-phenylacrylamide, alkylacrylamides, methacrylamide poly(ethylene glycol)amine hydrochloride, and combinations thereof; and combinations thereof.

[0022] According to a further aspect, the present invention relates to a method for preparing a polymer latex for an adhesive, preferably a polymer latex as described above, comprising the steps of: A method comprising polymerizing a mixture of ethylenically unsaturated monomers by free radical emulsion polymerization: Here, the mixture of ethylenically unsaturated monomers is (a) vinyl aromatic monomers, (b) a conjugated diene monomer, and (c) containing ethylenically unsaturated monomers having acid and / or hydroxyl functionality; The weight ratio of vinyl aromatic monomer (a) to conjugated diene monomer (b) ranges from 1.60 to 2.30, and the polymer latex has a median particle size of at least 220 nm.

[0023] The weight ratio of vinyl aromatic monomer (a) to conjugated diene monomer (b) may range from 1.70 to 2.10.

[0024] The sum of the vinyl aromatic monomer (a) and the conjugated diene monomer (b) may range from 85.0 to 99.0% by weight, preferably from 90.0 to 98.0% by weight, based on the total weight of the monomers in the monomer mixture.

[0025] The mixture of ethylenically unsaturated monomers may be (a) The monomer mixture may contain 40 to 80% by weight, preferably 50 to 75% by weight, and more preferably 55 to 70% by weight, of a vinyl aromatic monomer, based on the total weight of the monomers in the monomer mixture.

[0026] The vinyl aromatic monomer (a) may be selected from styrene, alpha-methylstyrene, vinyltoluene, and combinations thereof. The vinyl aromatic monomer (a) may be selected from styrene.

[0027] The mixture of ethylenically unsaturated monomers may be (b) The monomer mixture may contain 15 to 50% by weight, preferably 20 to 45% by weight, and more preferably 25 to 40% by weight of a conjugated diene monomer, based on the total weight of the monomers in the monomer mixture.

[0028] Conjugated diene monomers (b) are 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, 2,4-hexadiene, 1,3-octadiene, 2-methyl-1,3-pentadiene, 2,3-dimethyl-1,3-pentadiene, 3,4-dimethyl-1,3-hexadiene, 2,3-diethyl-1,3-butadiene, 4,5-diethyl-1,3-octadiene, 3-butyl-1,3-octadiene, 3,7-dimethyl-1,3,6-octatriene, 2-methyl-6-methylene-1,7-octadiene, 7-methyl-3-methylene-1, The conjugated diene monomer (b) may be selected from 6-octadiene, 1,3,7-octatriene, 2-ethyl-1,3-butadiene, 2-amyl-1,3-butadiene, 3,7-dimethyl-1,3,7-octatriene, 3,7-dimethyl-1,3,6-octatriene, 3,7,11-trimethyl-1,3,6,10-dodecatetraene, 7,11-dimethyl-3-methylene-1,6,10-dodecatriene, 2,6-dimethyl-2,4,6-octatriene, 2-phenyl-1,3-butadiene, 2-methyl-3-isopropyl-1,3-butadiene, 1,3-cyclohexadiene, myrcene, ocimene, farnesene, and combinations thereof. The conjugated diene monomer (b) may be selected from 1,3-butadiene, isoprene, and combinations thereof. The conjugated diene monomer (b) may be selected from 1,3-butadiene.

[0029] The mixture of ethylenically unsaturated monomers may be (c) The monomer mixture may contain 0.2 to 6.0% by weight, preferably 0.3 to 5.0% by weight, more preferably 0.5 to 4.0% by weight, of an ethylenically unsaturated monomer having an acid functionality and / or a hydroxyl functionality, based on the total weight of the monomers in the monomer mixture.

[0030] The ethylenically unsaturated monomer (c) having an acid functional group can be selected from ethylenically unsaturated carboxylic acid monomers, ethylenically unsaturated sulfonic acid monomers, ethylenically unsaturated phosphorus-containing acid monomers.The ethylenically unsaturated monomer (c) having an acid functional group can be selected from (meth)acrylic acid, crotonic acid, fumaric acid, itaconic acid, maleic acid, maleic anhydride, vinyl acetic acid, vinyl lactic acid, vinyl sulfonic acid, styrene sulfonic acid, 2-carboxyethyl (meth)acrylate, phenyl vinyl sulfonate, sodium 4-vinylbenzene sulfonate, 2-methyl-2-propene-1-sulfonic acid, 2-propene-1-sulfonic acid, 4-styrene sulfonic acid, 2-acrylamido-2-methyl-1-propane sulfonic acid, vinyl phosphonic acid, dimethyl vinyl phosphonate, diethyl vinyl phosphonate, diethyl allyl phosphonate, allyl phosphonic acid, and combinations thereof. The ethylenically unsaturated monomer having an acid functionality (c) may be selected from (meth)acrylic acid, itaconic acid, and combinations thereof.

[0031] The ethylenically unsaturated monomer (c) having a hydroxyl functional group can be selected from allyl alcohol, vinyl alcohol, N-methylol (meth)acrylamide, 1-penten-3-ol, hydroxyalkyl esters of ethylenically unsaturated acids, such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate and hydroxyethyl caprolactone acrylate, and combinations thereof. The ethylenically unsaturated monomer (c) having a hydroxyl functional group can be selected from hydroxyalkyl esters of ethylenically unsaturated acids, such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate and hydroxyethyl caprolactone acrylate. The ethylenically unsaturated monomer (c) having a hydroxyl functional group can be selected from hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl methacrylate, and combinations thereof.

[0032] The ethylenically unsaturated monomer (c) having an acid function and a hydroxy function may be selected from 3-allyloxy-2-hydroxy-1-propanesulfonic acid.

[0033] The weight ratio of vinyl aromatic monomer (a) to conjugated diene monomer (b) may range from 1.70 to 2.10.

[0034] The polymer latex may have a median particle size of at least 230 nm, preferably at least 250 nm.

[0035] The mixture of ethylenically unsaturated monomers may contain 0.05-3.0 wt%, preferably 0.10-2.0 wt%, more preferably 0.15-1.5 wt% of a chain transfer agent, where the weight percentage is based on the total amount of monomers in the monomer mixture. The chain transfer agent may be selected from n-dodecyl mercaptan, carbon tetrachloride, carbon tetrabromide, bromotrichloromethane, 4-methylbenzenethiol, isooctyl 3-mercaptopropionate, tert-nonyl mercaptan, 4,4'-thiobisbenzenethiol, tert-dodecyl mercaptan, α-methylstyrene dimer, thioglycolic acid, 2-ethylhexyl thioglycolate, butyl 3-mercaptopropionate, 1,8-dimercapto-3,6-dioxaoctane, and combinations thereof, preferably tert-dodecyl mercaptan.

[0036] The mixture of ethylenically unsaturated monomers may further comprise (d) 0 to 20% by weight of an ethylenically unsaturated monomer different from (a) to (c), based on the total weight of the monomers in the monomer mixture, and the ethylenically unsaturated monomer different from (a) to (c) is preferably (d1) an ethylenically unsaturated nitrile compound, preferably selected from (meth)acrylonitrile, alpha-cyanoethyl acrylonitrile, fumaronitrile, alpha-chloronitrile and combinations thereof; (d2) alkyl esters of ethylenically unsaturated acids, preferably selected from methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and combinations thereof; (d3) ethylenically unsaturated compounds having a primary or secondary amino group, preferably selected from (meth)acrylamide, 2-aminoethyl (meth)acrylate hydrochloride, 2-aminoethyl (meth)acrylamide hydrochloride, N-ethyl (meth)acrylamide, N-(3-aminopropyl) (meth)acrylamide hydrochloride, N-hydroxyethyl (meth)acrylamide, N-3-(dimethylamino)propyl (meth)acrylamide, [3-(methacryloylamino)propyl]trimethylammonium, N-[tris(hydroxymethyl)methyl] (meth)acrylamide, N-phenylacrylamide, alkylacrylamides, methacrylamide poly(ethylene glycol)amine hydrochloride, and combinations thereof; and combinations thereof.

[0037] Another aspect of the present invention relates to the use of a polymer latex as described above or prepared by the method as described above for the preparation of an aqueous adhesive composition, preferably a two-component aqueous adhesive composition.

[0038] Yet a further aspect of the present invention relates to an aqueous adhesive composition comprising (i) the polymer latex described above or the polymer latex prepared by the method described above, and (ii) a polyisocyanate compound.

[0039] (ii) Polyisocyanate compounds include toluene diisocyanate, hydrogenated toluene diisocyanate, methylene diphenyl diisocyanate, hydrogenated methylene diphenyl diisocyanate, triphenylmethane triisocyanate, 1,2,4-benzene triisocyanate, polymethylene polyphenyl polyisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, 1,6-hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, isophorone diisocyanate, and 4,4'-methylene-bis(cyclohexyl isocyanate), and combinations thereof.

[0040] The above-mentioned aqueous adhesive composition may further comprise polyvinyl alcohol, vinyl alcohol-ethylene copolymers, silanol-modified polyvinyl alcohol, cellulose derivatives such as methyl cellulose, ethyl cellulose, hydroxycellulose and carboxycellulose, chitin, chitosan, starch, polyethylene glycol, polypropylene glycol, polyvinyl ether, gelatin, casein, cyclodextrin, and combinations thereof, preferably polyvinyl alcohol.

[0041] The above-mentioned aqueous adhesive composition may be a two-component adhesive composition, the first component comprising the above-mentioned polymer latex and optionally polyvinyl alcohol, vinyl alcohol-ethylene copolymer, silanol-modified polyvinyl alcohol, cellulose derivatives such as methyl cellulose, ethyl cellulose, hydroxycellulose and carboxycellulose, chitin, chitosan, starch, polyethylene glycol, polypropylene glycol, polyvinyl ether, gelatin, casein, cyclodextrin, and combinations thereof, preferably polyvinyl alcohol, and the second component comprising a polyisocyanate compound.

[0042] The above-mentioned aqueous adhesive composition can contain 1 to 50% by weight, preferably 2 to 45% by weight, and more preferably 5 to 40% by weight of the polyisocyanate compound (ii) based on the total solid content of the aqueous adhesive composition.

[0043] The water-based adhesives mentioned above may be in the form of wood adhesives.

[0044] Another aspect of the present invention relates to a method for preparing an aqueous adhesive composition, the method comprising: (i) providing a polymer latex as described above or prepared by the method as described above, and (ii) mixing with a polyisocyanate compound, wherein the aqueous adhesive composition is preferably a wood adhesive. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] The present invention relates to a polymer latex for use in an adhesive composition. The polymer latex may be obtained by free radical emulsion polymerization of a mixture of ethylenically unsaturated monomers including (a) vinyl aromatic monomers, (b) conjugated diene monomers, and (c) ethylenically unsaturated monomers having acid and / or hydroxyl functionality. According to the present invention, the weight ratio of the vinyl aromatic monomers (a) to the conjugated diene monomers (b) is in the range of 1.60 to 2.30. The polymer latex of the present invention has a median particle size of at least 220 nm. The median particle size may be measured by dynamic light scattering according to ISO 22412:2017, for example using a dynamic light scattering instrument Mastersizer 2000 (Malvern Panalytical, UK). The polymer latex is preferably obtained by free radical emulsion polymerization of a mixture of ethylenically unsaturated monomers including (a) vinyl aromatic monomers, (b) conjugated diene monomers, and (c) ethylenically unsaturated monomers having acid and / or hydroxyl functionality.

[0046] Surprisingly, it has been found that the weight ratio of vinyl aromatic monomer (a) to conjugated diene monomer (b) and median particle size of the polymer latex of the present invention improves wood bond strength and pot life.

[0047] According to the present invention, the sum of vinyl aromatic monomer (a) and conjugated diene monomer (b) can be at least 85.0 wt%, for example at least 87.0 wt%, at least 90.0 wt%, at least 93.0 wt%, at least 95.0 wt%, or at least 97.0 wt%, based on the total weight of monomers in the monomer mixture. The sum of vinyl aromatic monomer (a) and conjugated diene monomer (b) can be 99.0 wt% or less, for example 98.5 wt% or less, 98.0 wt% or less, or 97.5 wt% or less, based on the total weight of monomers in the monomer mixture. Those skilled in the art will understand that any range between any of the explicitly disclosed lower and upper limits is disclosed herein. Thus, the sum of the vinyl aromatic monomer (a) and the conjugated diene monomer (b) may be in the range of 85.0 to 99.0% by weight, preferably 90.0 to 98.0% by weight, more preferably 92.0 to 98% by weight, even more preferably 95.0 to 98.0% by weight, and most preferably 95.0 to 98.0% by weight, based on the total weight of the monomers in the monomer mixture.

[0048] The mixture of ethylenically unsaturated monomers of the present invention can comprise (a) at least 40% by weight, e.g., at least 43% by weight, at least 45% by weight, at least 47% by weight, at least 50% by weight, at least 53% by weight, at least 55% by weight, at least 57% by weight, or at least 60% by weight of vinyl aromatic monomer, based on the total weight of monomers in the monomer mixture. The mixture of ethylenically unsaturated monomers of the present invention can comprise (a) 80% by weight or less, e.g., 78% by weight or less, 75% by weight or less, 70% by weight or less, or 68% by weight or less of vinyl aromatic monomer, based on the total weight of monomers in the monomer mixture. One skilled in the art will understand that any range between any of the explicitly disclosed lower and upper limits is disclosed herein. Thus, the mixture of ethylenically unsaturated monomers can comprise (a) 40-80% by weight, preferably 50-75% by weight, more preferably 55-70% by weight, and most preferably 60-70% by weight of vinyl aromatic monomer, based on the total weight of monomers in the monomer mixture.

[0049] According to the present invention, the vinyl aromatic monomer (a) may be selected from styrene, α-methylstyrene, vinyltoluene and combinations thereof. Preferably, the vinyl aromatic monomer (a) may be styrene.

[0050] The mixture of ethylenically unsaturated monomers of the present invention can comprise (b) at least 15% by weight, e.g., at least 17% by weight, at least 20% by weight, at least 22% by weight, at least 25% by weight, at least 27% by weight, or at least 30% by weight of conjugated diene monomers, based on the total weight of the monomers in the monomer mixture. The mixture of ethylenically unsaturated monomers of the present invention can comprise (b) 50% by weight or less, e.g., 48% by weight or less, 45% by weight or less, 43% by weight or less, 40% by weight or less, or 38% by weight or less of conjugated diene monomers, based on the total weight of the monomers in the monomer mixture. One of ordinary skill in the art will understand that any range between any of the explicitly disclosed lower and upper limits is disclosed herein. Thus, the mixture of ethylenically unsaturated monomers can comprise (b) 15-50% by weight, preferably 20-45% by weight, more preferably 25-40% by weight, even more preferably 27-40% by weight, and most preferably 27-38% by weight of conjugated diene monomers, based on the total weight of the monomers in the monomer mixture.

[0051] According to the present invention, the conjugated diene monomer (b) is selected from the group consisting of 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, 2,4-hexadiene, 1,3-octadiene, 2-methyl-1,3-pentadiene, 2,3-dimethyl-1,3-pentadiene, 3,4-dimethyl-1,3-hexadiene, 2,3-diethyl-1,3-butadiene, 4,5-diethyl-1,3-octadiene, 3-butyl-1,3-octadiene, 3,7-dimethyl-1,3,6-octatriene, 2-methyl-6-methylene-1,7-octadiene, 7-methyl-3-methylene-1,6-octadiene, 1,3 The conjugated diene monomer (b) may be selected from 1,3-butadiene, 2-ethyl-1,3-butadiene, 2-amyl-1,3-butadiene, 3,7-dimethyl-1,3,7-octatriene, 3,7-dimethyl-1,3,6-octatriene, 3,7,11-trimethyl-1,3,6,10-dodecatetraene, 7,11-dimethyl-3-methylene-1,6,10-dodecatriene, 2,6-dimethyl-2,4,6-octatriene, 2-phenyl-1,3-butadiene, 2-methyl-3-isopropyl-1,3-butadiene, 1,3-cyclohexadiene, myrcene, ocimene, farnesene and combinations thereof, preferably 1,3-butadiene, isoprene and combinations thereof. The conjugated diene monomer (b) may be 1,3-butadiene.

[0052] The mixture of ethylenically unsaturated monomers of the present invention may comprise (c) at least 0.2% by weight, for example at least 0.3% by weight, at least 0.4% by weight, at least 0.5% by weight, at least 0.6% by weight, at least 0.7% by weight, at least 0.8% by weight, at least 0.9% by weight, or at least 1.0% by weight of ethylenically unsaturated monomers having acid and / or hydroxyl functional groups, based on the total weight of monomers in the monomer mixture. The mixture of ethylenically unsaturated monomers of the present invention may comprise (c) no more than 6.0% by weight, for example no more than 5.5% by weight, no more than 5.0% by weight, no more than 4.5% by weight, or no more than 4.0% by weight of ethylenically unsaturated monomers having acid and / or hydroxyl functional groups, based on the total weight of monomers in the monomer mixture. One skilled in the art will understand that any range between any of the explicitly disclosed lower and upper limits is disclosed herein. Thus, the mixture of ethylenically unsaturated monomers may comprise (c) 0.2 to 6.0 wt. %, preferably 0.3 to 5.0 wt. %, more preferably 0.5 to 4.0 wt. %, even more preferably 0.7 to 4.0 wt. %, and most preferably 1.0 to 4.0 wt. % of ethylenically unsaturated monomers having acid and / or hydroxyl functionality, based on the total weight of the monomers in the monomer mixture.

[0053] The ethylenically unsaturated monomers (c) having acid functionality that can be used in the present invention can be selected from ethylenically unsaturated carboxylic acid monomers, ethylenically unsaturated sulfonic acid monomers, ethylenically unsaturated phosphorus-containing acid monomers, and combinations thereof. Ethylenically unsaturated carboxylic acid monomers suitable for use in the present invention include mono- and dicarboxylic acid monomers, monoesters of dicarboxylic acids, and carboxyalkyl esters of ethylenically unsaturated acids such as 2-carboxyethyl (meth)acrylate, and ethylenically unsaturated carboxylic acid derivatives such as ethylenically unsaturated dicarboxylic acid anhydrides. In carrying out the present invention, it is preferred to use ethylenically unsaturated aliphatic mono- or dicarboxylic acids or anhydrides containing 3 to 5 carbon atoms. Examples of monocarboxylic acid monomers include (meth)acrylic acid, crotonic acid, and examples of dicarboxylic acid monomers include fumaric acid, itaconic acid, maleic acid, and maleic anhydride.

[0054] Examples of ethylenically unsaturated sulfonic acid monomers include vinyl sulfonic acid, phenyl vinyl sulfonate, sodium 4-vinylbenzenesulfonate, 2-methyl-2-propene-1-sulfonic acid, 2-propene-1-sulfonic acid, 4-styrenesulfonic acid, 3-allyloxy-2-hydroxy-1-propanesulfonic acid, 2-acrylamido-2-methyl-1-propanesulfonic acid, and salts thereof.

[0055] Examples of ethylenically unsaturated phosphorus-containing acid monomers include vinyl phosphonic acid, dimethyl vinyl phosphonate, diethyl vinyl phosphonate, diethyl allyl phosphonate, allyl phosphonic acid, and salts thereof.

[0056] Preferably, the ethylenically unsaturated monomer (c) having an acid functional group is selected from ethylenically unsaturated carboxylic acid monomers, ethylenically unsaturated sulfonic acid monomers, ethylenically unsaturated phosphorus-containing acid monomers, and combinations thereof, and is preferably selected from (meth)acrylic acid, crotonic acid, fumaric acid, itaconic acid, maleic acid, maleic anhydride, vinyl acetic acid, vinyl lactic acid, vinyl sulfonic acid, styrene sulfonic acid, 2-carboxyethyl (meth)acrylate, phenyl vinyl sulfonate, sodium 4-vinylbenzene sulfonate, 2-methyl-2-propene-1-sulfonic acid, 2-propene-1-sulfonic acid, 4-styrene sulfonic acid, 2-acrylamido-2-methyl-1-propane sulfonic acid, vinyl phosphonic acid, dimethyl vinyl phosphonate, diethyl vinyl phosphonate, diethyl allyl phosphonate, allyl phosphonic acid, and combinations thereof.More preferably, the ethylenically unsaturated monomer (c) having an acid functional group is selected from (meth)acrylic acid, itaconic acid, and combinations thereof.

[0057] The ethylenically unsaturated monomer (c) having a hydroxyl functionality that can be used in the present invention can be selected from allyl alcohol, vinyl alcohol, N-methylol (meth)acrylamide, 1-penten-3-ol, hydroxyalkyl esters of ethylenically unsaturated acids and combinations thereof, preferably hydroxyalkyl esters of ethylenically unsaturated acids.

[0058] Hydroxyalkyl esters of ethylenically unsaturated acids include hydroxyalkyl acrylate and hydroxyalkyl methacrylate monomers based on ethylene oxide, propylene oxide and higher alkylene oxides or mixtures thereof. Suitable examples of hydroxyalkyl esters of ethylenically unsaturated acids can be selected from hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, hydroxyethyl caprolactone acrylate, and combinations thereof.

[0059] The ethylenically unsaturated monomers (c) having acid and hydroxyl functions that can be used in the present invention can be selected from 3-allyloxy-2-hydroxy-1-propanesulfonic acids.

[0060] Ethylenically unsaturated monomers (c) having acid and / or hydroxyl functional groups that can be used in the present invention are (meth)acrylic acid, crotonic acid, fumaric acid, itaconic acid, maleic acid, maleic anhydride, vinylacetic acid, vinyllactic acid, vinylsulfonic acid, styrenesulfonic acid, 2-carboxyethyl (meth)acrylate, phenyl vinylsulfonate, sodium 4-vinylbenzenesulfonate, 2-methyl-2-propene-1-sulfonic acid, 2-propene-1-sulfonic acid, 4-styrenesulfonic acid, 2-acrylamido-2-methyl-1-propanesulfonic acid, vinylphosphonic acid, dimethyl vinylphosphonate, diethyl vinylphosphonate, diethyl allylphosphonate, allylphosphonic acid, allyl alcohol, vinyl alcohol, N-methylol (meth)acrylamide, 1-penten-3-ol, hydroxyalkyl esters of ethylenically unsaturated acids, The hydroxyalkyl ester of an ethylenically unsaturated acid may be selected from, for example, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, and hydroxyethyl caprolactone acrylate, and 3-allyloxy-2-hydroxy-1-propanesulfonic acid, preferably from (meth)acrylic acid, itaconic acid, hydroxyalkyl ester of an ethylenically unsaturated acid, for example, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, and hydroxyethyl caprolactone acrylate, and combinations thereof, more preferably from (meth)acrylic acid, itaconic acid, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, and combinations thereof.

[0061] In accordance with the present invention, the mixture of ethylenically unsaturated monomers comprises, based on the total weight of the monomers in the monomer mixture: (a) 40 to 80% by weight, preferably 50 to 75% by weight, more preferably 55 to 70% by weight, and most preferably 60 to 70% by weight of vinyl aromatic monomer; (b) 15 to 50% by weight, preferably 20 to 45% by weight, more preferably 25 to 40% by weight, even more preferably 27 to 40% by weight, and most preferably 27 to 38% by weight of a conjugated diene monomer; and (c) 0.2 to 6.0% by weight, preferably 0.3 to 5.0% by weight, more preferably 0.5 to 4.0% by weight, even more preferably 0.7 to 4.0% by weight, and most preferably 1.0 to 4.0% by weight of an ethylenically unsaturated monomer having an acid functional group and / or a hydroxyl functional group.

[0062] In accordance with the present invention, the mixture of ethylenically unsaturated monomers comprises, based on the total weight of the monomers in the monomer mixture: (a) 40 to 80% by weight, preferably 50 to 75% by weight, more preferably 55 to 70% by weight, and most preferably 60 to 70% by weight of vinyl aromatic monomer; (b) 15 to 50% by weight, preferably 20 to 45% by weight, more preferably 25 to 40% by weight, even more preferably 27 to 40% by weight, and most preferably 27 to 38% by weight of a conjugated diene monomer; and (c) 0.2 to 6.0% by weight, preferably 0.3 to 5.0% by weight, more preferably 0.5 to 4.0% by weight, even more preferably 0.7 to 4.0% by weight, and most preferably 1.0 to 4.0% by weight of an ethylenically unsaturated monomer having an acid functional group and / or a hydroxyl functional group, wherein the vinyl aromatic monomer (a) may be selected from styrene, α-methylstyrene, vinyltoluene and combinations thereof, preferably styrene; Conjugated diene monomers (b) are 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, 2,4-hexadiene, 1,3-octadiene, 2-methyl-1,3-pentadiene, 2,3-dimethyl-1,3-pentadiene, 3,4-dimethyl-1,3-hexadiene, 2,3-diethyl-1,3-butadiene, 4,5-diethyl-1,3-octadiene, 3-butyl-1,3-octadiene, 3,7-dimethyl-1,3,6-octatriene, 2-methyl-6-methylene-1,7-octadiene, 7-methyl-3-methylene-1,6-octadiene, 1,3,7-octatriene, 2 -ethyl-1,3-butadiene, 2-amyl-1,3-butadiene, 3,7-dimethyl-1,3,7-octatriene, 3,7-dimethyl-1,3,6-octatriene, 3,7,11-trimethyl-1,3,6,10-dodecatetraene, 7,11-dimethyl-3-methylene-1,6,10-dodecatriene, 2,6-dimethyl-2,4,6-octatriene, 2-phenyl-1,3-butadiene, 2-methyl-3-isopropyl-1,3-butadiene, 1,3-cyclohexadiene, myrcene, ocimene, farnesene and combinations thereof, preferably 1,3-butadiene, isoprene and combinations thereof, more preferably 1,3-butadiene; Ethylenically unsaturated monomers (c) having acid and / or hydroxyl functional groups are (meth)acrylic acid, crotonic acid, fumaric acid, itaconic acid, maleic acid, maleic anhydride, vinyl acetic acid, vinyl lactic acid, vinyl sulfonic acid, styrene sulfonic acid, 2-carboxyethyl (meth)acrylate, phenyl vinyl sulfonate, sodium 4-vinylbenzene sulfonate, 2-methyl-2-propene-1-sulfonic acid, 2-propene-1-sulfonic acid, 4-styrene sulfonic acid, 2-acrylamido-2-methyl-1-propane sulfonic acid, vinyl phosphonic acid, dimethyl vinyl phosphonate, diethyl vinyl phosphonate, diethyl allyl phosphonate, allyl phosphonic acid, allyl alcohol, vinyl alcohol, N-methylol (meth)acrylamide, 1-penten-3-ol, hydroxyalkyl esters of ethylenically unsaturated acids, e.g. hydo The alkyl ester may be selected from hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate and hydroxyethyl caprolactone acrylate, and 3-allyloxy-2-hydroxy-1-propanesulfonic acid, preferably from (meth)acrylic acid, itaconic acid, hydroxyalkyl esters of ethylenically unsaturated acids, such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate and hydroxyethyl caprolactone acrylate, and combinations thereof, more preferably from (meth)acrylic acid, itaconic acid, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate and hydroxyethyl caprolactone acrylate, and combinations thereof.

[0063] According to the present invention, the weight ratio of vinyl aromatic monomer (a) to conjugated diene monomer (b) is at least 1.60, such as at least 1.62, at least 1.65, at least 1.67, or at least 1.70. The weight ratio of vinyl aromatic monomer (a) to conjugated diene monomer (b) is 2.30 or less, such as 2.25 or less, 2.20 or less, 2.15 or less, or 2.10 or less. A person skilled in the art will understand that any range between any of the explicitly disclosed lower and upper limits is disclosed herein. Thus, the weight ratio of vinyl aromatic monomer (a) to conjugated diene monomer (b) may range from 1.62 to 2.25, preferably from 1.65 to 2.20, more preferably from 1.70 to 2.15, and most preferably from 1.70 to 2.10.

[0064] According to the present invention, the polymer latex has a median particle size of at least 220 nm, preferably at least 230 nm, more preferably at least 250 nm. The polymer latex can have a median particle size of 400 nm or less, such as 350 nm or less, or 300 nm or less. A person skilled in the art will understand that any range between any of the explicitly disclosed lower and upper limits is disclosed herein. Thus, the polymer latex can have a median particle size ranging from 220 nm to 400 nm, preferably 230 nm to 400 nm, more preferably 250 nm to 400 nm. The median particle size can be measured by dynamic light scattering according to ISO22412:2017, for example using a dynamic light scattering instrument Mastersizer 2000 (manufactured by Malvern Panalytical (UK)).

[0065] The mixture of ethylenically unsaturated monomers may include a chain transfer agent. According to the present invention, the mixture of ethylenically unsaturated monomers may include at least 0.05 wt%, e.g., at least 0.07 wt%, at least 0.10 wt%, at least 0.12 wt%, or at least 0.15 wt% of a chain transfer agent, where the weight percentage is based on the total amount of monomers in the monomer mixture. The mixture of ethylenically unsaturated monomers may include 3.0 wt% or less, e.g., 2.5 wt% or less, 2.0 wt% or less, or 1.5 wt% or less of a chain transfer agent, where the weight percentage is based on the total amount of monomers in the monomer mixture. One of ordinary skill in the art will understand that any range between any of the explicitly disclosed lower and upper limits is disclosed herein. Thus, the mixture of ethylenically unsaturated monomers may include 0.05 to 3.0 wt%, preferably 0.10 to 2.0 wt%, more preferably 0.15 to 1.5 wt% of a chain transfer agent, where the weight percentage is based on the total amount of monomers in the monomer mixture.

[0066] The chain transfer agent may be selected from n-dodecyl mercaptan, carbon tetrachloride, carbon tetrabromide, bromotrichloromethane, 4-methylbenzenethiol, isooctyl 3-mercaptopropionate, tert-nonyl mercaptan, 4,4'-thiobisbenzenethiol, tert-dodecyl mercaptan, α-methylstyrene dimer, thioglycolic acid, 2-ethylhexyl thioglycolate, butyl 3-mercaptopropionate, 1,8-dimercapto-3,6-dioxaoctane and combinations thereof, more preferably tert-dodecyl mercaptan.

[0067] The mixture of ethylenically unsaturated monomers may further contain (d) an ethylenically unsaturated monomer different from (a) to (c). According to the present invention, the mixture of ethylenically unsaturated monomers may further contain (d) 0 to 20% by weight, preferably 0 to 15% by weight, more preferably 0 to 10% by weight, of an ethylenically unsaturated monomer different from (a) to (c), based on the total weight of the monomers in the monomer mixture. The ethylenically unsaturated monomer different from (a) to (c) may be selected from (d1) an ethylenically unsaturated nitrile compound, (d2) an alkyl ester of an ethylenically unsaturated acid, (d3) an ethylenically unsaturated compound having a primary or secondary amino group, and a combination thereof.

[0068] The ethylenically unsaturated nitrile compound (d1) may be selected from (meth)acrylonitrile, α-cyanoethylacrylonitrile, fumaronitrile, α-chloronitrile, and combinations thereof.

[0069] The alkyl ester of an ethylenically unsaturated acid (d2) may be selected from methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and combinations thereof, preferably methyl (meth)acrylate and combinations thereof.

[0070] The ethylenically unsaturated compound having a primary or secondary amino group (d3) may be selected from (meth)acrylamide, 2-aminoethyl (meth)acrylate hydrochloride, 2-aminoethyl (meth)acrylamide hydrochloride, N-ethyl (meth)acrylamide, N-(3-aminopropyl) (meth)acrylamide hydrochloride, N-hydroxyethyl (meth)acrylamide, N-3-(dimethylamino)propyl (meth)acrylamide, [3-(methacryloylamino)propyl]trimethylammonium, N-[tris(hydroxymethyl)methyl] (meth)acrylamide, N-phenylacrylamide, alkylacrylamides, methacrylamide poly(ethylene glycol)amine hydrochloride, and combinations thereof.

[0071] According to the present invention, the amounts of the monomers defined above for the preparation of the polymer latex may total 100% by weight, based on the total amount of monomers in the monomer mixture.

[0072] Method for preparing polymer latex The present invention relates to a method for preparing a polymer latex for use in an adhesive, comprising polymerizing by free radical emulsion polymerization a mixture of ethylenically unsaturated monomers, the mixture of ethylenically unsaturated monomers comprising (a) a vinyl aromatic monomer, (b) a conjugated diene monomer, and (c) an ethylenically unsaturated monomer having acid and / or hydroxyl functionality. According to the present invention, the weight ratio of the vinyl aromatic monomer (a) to the conjugated diene monomer (b) is in the range of 1.60 to 2.30. The polymer latex of the present invention has a median particle size of at least 220 nm. The median particle size can be measured by dynamic light scattering according to ISO 22412:2017, for example using a dynamic light scattering instrument Mastersizer 2000 (Malvern Panalytical, UK).

[0073] According to the present invention, the sum of vinyl aromatic monomer (a) and conjugated diene monomer (b) can be at least 85.0 wt%, for example at least 87.0 wt%, at least 90.0 wt%, at least 93.0 wt%, at least 95.0 wt%, or at least 97.0 wt%, based on the total weight of monomers in the monomer mixture. The sum of vinyl aromatic monomer (a) and conjugated diene monomer (b) can be 99.0 wt% or less, for example 98.5 wt% or less, 98.0 wt% or less, or 97.5 wt% or less, based on the total weight of monomers in the monomer mixture. Those skilled in the art will understand that any range between any of the explicitly disclosed lower and upper limits is disclosed herein. Thus, the sum of the vinyl aromatic monomer (a) and the conjugated diene monomer (b) may be in the range of 85.0 to 99.0 wt%, preferably 90.0 to 98.0 wt%, more preferably 92.0 to 98.0 wt%, even more preferably 95.0 to 98.0 wt%, and most preferably 95.0 to 98.0 wt%, based on the total weight of the monomers in the monomer mixture.

[0074] All variations in the compounds used in preparing the polymer latex of the present invention and their relative amounts may be as described above.

[0075] According to the present invention, the weight ratio of vinyl aromatic monomer (a) to conjugated diene monomer (b) is at least 1.60, such as at least 1.62, at least 1.65, at least 1.67, or at least 1.70. The weight ratio of vinyl aromatic monomer (a) to conjugated diene monomer (b) is 2.30 or less, such as 2.25 or less, 2.20 or less, 2.15 or less, or 2.10 or less. A person skilled in the art will understand that any range between any of the explicitly disclosed lower and upper limits is disclosed herein. Thus, the weight ratio of vinyl aromatic monomer (a) to conjugated diene monomer (b) may range from 1.62 to 2.25, preferably from 1.65 to 2.20, more preferably from 1.70 to 2.15, and most preferably from 1.70 to 2.10.

[0076] According to the present invention, the polymer latex has a median particle size of at least 220 nm, preferably at least 230 nm, more preferably at least 250 nm. The polymer latex can have a median particle size of 400 nm or less, such as 350 nm or less, or 300 nm or less. A person skilled in the art will understand that any range between any of the explicitly disclosed lower and upper limits is disclosed herein. Thus, the polymer latex can have a median particle size ranging from 220 nm to 400 nm, preferably 230 nm to 400 nm, more preferably 250 nm to 400 nm. The median particle size can be measured by dynamic light scattering according to ISO22412:2017, for example using a dynamic light scattering instrument Mastersizer 2000 (manufactured by Malvern Panalytical (UK)).

[0077] The mixture of ethylenically unsaturated monomers may include a chain transfer agent. According to the present invention, the mixture of ethylenically unsaturated monomers may include at least 0.05 wt%, e.g., at least 0.07 wt%, at least 0.10 wt%, at least 0.12 wt%, or at least 0.15 wt% of a chain transfer agent, where the weight percentage is based on the total amount of monomers in the monomer mixture. The mixture of ethylenically unsaturated monomers may include 3.0 wt% or less, e.g., 2.5 wt% or less, 2.0 wt% or less, or 1.5 wt% or less of a chain transfer agent, where the weight percentage is based on the total amount of monomers in the monomer mixture. One of ordinary skill in the art will understand that any range between any of the explicitly disclosed lower and upper limits is disclosed herein. Thus, the mixture of ethylenically unsaturated monomers may include 0.05 to 3.0 wt%, preferably 0.10 to 2.0 wt%, more preferably 0.15 to 1.5 wt% of a chain transfer agent, where the weight percentage is based on the total amount of monomers in the monomer mixture.

[0078] The chain transfer agent may be selected from n-dodecyl mercaptan, carbon tetrachloride, carbon tetrabromide, bromotrichloromethane, 4-methylbenzenethiol, isooctyl 3-mercaptopropionate, tert-nonyl mercaptan, 4,4'-thiobisbenzenethiol, tert-dodecyl mercaptan, α-methylstyrene dimer, thioglycolic acid, 2-ethylhexyl thioglycolate, butyl 3-mercaptopropionate, 1,8-dimercapto-3,6-dioxaoctane and combinations thereof, more preferably tert-dodecyl mercaptan.

[0079] The mixture of ethylenically unsaturated monomers may further contain (d) an ethylenically unsaturated monomer different from (a) to (c). According to the present invention, the mixture of ethylenically unsaturated monomers may further contain (d) 0 to 20% by weight, preferably 0 to 15% by weight, more preferably 0 to 10% by weight, of an ethylenically unsaturated monomer different from (a) to (c), based on the total weight of the monomers in the monomer mixture. The ethylenically unsaturated monomer different from (a) to (c) may be selected from (d1) an ethylenically unsaturated nitrile compound, (d2) an alkyl ester of an ethylenically unsaturated acid, (d3) an ethylenically unsaturated compound having a primary or secondary amino group, and a combination thereof.

[0080] The ethylenically unsaturated nitrile compound (d1) may be selected from (meth)acrylonitrile, α-cyanoethylacrylonitrile, fumaronitrile, α-chloronitrile, and combinations thereof.

[0081] The alkyl ester of an ethylenically unsaturated acid (d2) may be selected from methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and combinations thereof, preferably methyl (meth)acrylate and combinations thereof.

[0082] The ethylenically unsaturated compound having a primary or secondary amino group (d3) may be selected from (meth)acrylamide, 2-aminoethyl (meth)acrylate hydrochloride, 2-aminoethyl (meth)acrylamide hydrochloride, N-ethyl (meth)acrylamide, N-(3-aminopropyl) (meth)acrylamide hydrochloride, N-hydroxyethyl (meth)acrylamide, N-3-(dimethylamino)propyl (meth)acrylamide, [3-(methacryloylamino)propyl]trimethylammonium, N-[tris(hydroxymethyl)methyl] (meth)acrylamide, N-phenylacrylamide, alkylacrylamides, methacrylamide poly(ethylene glycol)amine hydrochloride, and combinations thereof.

[0083] According to the present invention, the amounts of the monomers defined above for the preparation of the polymer latex may total 100% by weight, based on the total amount of monomers in the monomer mixture.

[0084] The polymer latex of the present invention can be made by any emulsion polymerization process known to those skilled in the art, provided that the monomer mixtures defined herein are used.

[0085] A seed dispersion can be used in the emulsion polymerization to prepare the polymer latex of the present invention. Any seed particles known to those skilled in the art can be used.

[0086] The seed particles are preferably present in an amount of 0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the total ethylenically unsaturated monomers used in the polymer. Thus, the lower limit of the amount of seed particles can be 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4 or 2.5 parts by weight. The upper limit of the amount can be 10, 9, 8, 7, 6, 5.5, 5, 4.5, 4, 3.8, 3.6, 3.4, 3.3, 3.2, 3.1 or 3 parts by weight. One of ordinary skill in the art will understand that any range formed by any of the explicitly disclosed lower and upper limits is expressly encompassed herein.

[0087] The above-mentioned process for the preparation of the polymer latex can be carried out in the presence or absence of one or more emulsifiers, in the presence or absence of one or more protective colloids and in the presence of one or more initiators at temperatures of 0 to 130° C., preferably 0 to 100° C., particularly preferably 20 to 95° C., very particularly preferably 40 to 90° C., including all values ​​and subvalues ​​therebetween, in particular 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120 and 125° C.

[0088] The initiator that can be used in carrying out the present invention can include water-soluble and / or oil-soluble initiators that are effective for polymerization purposes.Representative initiators are well known in the art, and include, for example, azo compounds (such as AIBN, AMBN, and cyanovaleric acid), inorganic peroxy compounds (such as hydrogen peroxide, sodium peroxydisulfate, potassium peroxydisulfate, and ammonium peroxydisulfate, peroxycarbonates, and peroxyborates), organic peroxy compounds (such as alkyl hydroperoxides, dialkyl peroxides, acyl hydroperoxides, and diacyl peroxides), and esters (such as tertiary butyl perbenzoate), as well as combinations of inorganic and organic initiators. Suitable initiators include 2,3-dimethyl-2,3-diphenylbutane, tert-butyl hydroperoxide, tert-amyl hydroperoxide, cumyl hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, isopropyl cumyl hydroperoxide, p-menthane hydroperoxide, 2,5-di(tert-butylperoxy)-2,5-dimethyl-3-hexyne, 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxanane, di(tert-butyl)peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, di(tert-butylperoxyisopropyl)benzene, tert-butylcumyl peroxide, di-(tert-amyl) -peroxide, dicumyl peroxide, butyl 4,4-di(tert-butylperoxy)valerate, tert-butylperoxybenzoate, 2,2-di(tert-butylperoxy)butane, tert-amyl peroxybenzoate, tert-butylperoxyacetate, tert-butylperoxy-(2-ethylhexyl)carbonate, tert-butylperoxyisopropylcarbonate, tert-butylperoxy-3,5,5-trimethyl-hexanoate, 1,1-di(tert-butylperoxy)cyclohexane, tert-amyl peroxyacetate, tert-amylperoxy-(2-ethylhexyl)carbonate, 1,1-di(tert-butylperoxy)-3,5,5-Trimethylcyclohexane, 1,1-di(tert-amylperoxy)cyclohexane, tert-butyl monoperoxy maleate, 1,1'-azodi(hexahydrobenzonitrile), tert-butyl peroxy isobutyrate, tert-butyl peroxy diethyl acetate, tert-butyl peroxy 2-ethylhexanoate, dibenzoyl peroxide, tert-amyl peroxy 2-ethylhexanoate, di(4 -methylbenzoyl) peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, ammonium peroxodisulfate, 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane, 2,2'-azodi(2-methylbutyronitrile), 2,2'-azodi(isobutyronitrile), didecanoyl peroxide, potassium persulfate, dilauroyl peroxide, di(3,5,5-trimethylhexanoyl) peroxydicarbonate, di(2-ethylhexyl)peroxydicarbonate, di(4-tert-butylcyclohexyl)peroxydicarbonate, diisopropyl peroxydicarbonate, tert-butyl peroxyneodecanoate, di-sec-butyl peroxydicarbonate, tert-amyl peroxyneodecanoate, cumyl peroxyneoheptanoate, di(3-methoxybutyl)peroxydicarbonate, 1,1,3,3-tetramethylbutyl peroxyneodecanoate, cumyl peroxyneodecanoate, diisobutyryl peroxide, and mixtures thereof. ,

[0089] The initiator may be used in an amount sufficient to initiate the polymerization reaction at the desired rate. Generally, an amount of initiator between 0.01 and 5 weight percent, preferably between 0.1 and 4 weight percent, based on the total weight of the monomers in the monomer mixture, is sufficient. The amount of initiator is most preferably between 0.01 and 2 weight percent, based on the total weight of the monomers in the monomer mixture. The amount of initiator includes all values ​​and subvalues ​​therebetween, particularly including 0.01, 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 4 and 4.5 weight percent, based on the total weight of the monomers in the monomer mixture.

[0090] The above inorganic and organic peroxy compounds may also be used alone or in combination with one or more suitable reducing agents, as is well known in the art. Examples of such reducing agents include sulfur dioxide, alkali metal disulfites, alkali metal and ammonium hydrogen sulfites, thiosulfates, dithionite and formaldehyde sulfoxylates, hydroxylamine hydrochloride, hydrazine sulfate, iron(II) sulfate, copper naphthenate, glucose, sulfonic acid compounds such as sodium methanesulfonate, amine compounds such as dimethylaniline, and ascorbic acid. The amount of reducing agent is preferably 0.03 to 10 parts by weight per part by weight of the polymerization initiator.

[0091] Suitable surfactants or emulsifiers for stabilizing the dispersed polymer include conventional surfactants for polymerization processes. Surfactants can be added to the aqueous phase and / or the monomer phase. The effective amount of surfactant in the seeded process is the amount selected to support colloidal stabilization of the particles, minimizing interparticle contact and preventing agglomeration. In the non-seeded process, the effective amount of surfactant is the amount selected to determine particle size.

[0092] Representative surfactants include, for example, saturated and ethylenically unsaturated sulfonic acids or their salts, such as unsaturated hydrocarbon sulfonic acids and their salts, such as vinyl sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, etc.; aromatic hydrocarbon acids and their salts, such as p-styrene sulfonic acid, isopropenyl benzene sulfonic acid, vinyloxybenzene sulfonic acid, etc.; sulfoalkyl esters of acrylic and methacrylic acid, such as sulfoethyl methacrylate and sulfopropyl methacrylate and their salts, and 2-acrylamido-2-methylpropane sulfonic acid and its salts; alkylated diphenyloxide disulfonates, sodium dodecylbenzene sulfonate, dihexyl or dioctyl esters of sodium sulfosuccinate, sodium alkyl esters of sulfonic acids, ethoxylated alkylphenols, and ethoxylated alcohols; and fatty alcohol sulfates and fatty alcohol (poly)ether sulfates.

[0093] The type and amount of surfactant typically depends on the number of particles, their size and their composition. Typically, surfactants are used in an amount of 0-20% by weight, preferably 0-10% by weight, more preferably 0-5% by weight, based on the total weight of monomers in the monomer mixture. The amount of surfactant includes all values ​​and subvalues ​​therebetween, including in particular 0, 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18 and 19% by weight, based on the total weight of monomers in the monomer composition. The polymerization can be carried out without surfactants.

[0094] The polymer latex of the present invention may further comprise a protective colloid. The protective colloid may include polyvinyl alcohol, vinyl alcohol-ethylene copolymer, silanol modified polyvinyl alcohol, cellulose derivatives such as methyl cellulose, ethyl cellulose, hydroxycellulose and carboxycellulose, chitin, chitosan, starch, polyethylene glycol, polypropylene glycol, polyvinyl ether, gelatin, casein, cyclodextrin, and combinations thereof. The protective colloid may stabilize the polymer latex in addition to or in place of the above surfactants. The protective colloid may be present during polymerization or may be added later. A typical amount is 1 to 15 parts by weight based on 100 parts by weight of the polymer latex.

[0095] Water-Based Adhesive Composition The present invention relates to the use of the polymer latex of the present invention as described above or prepared by the method of the present invention as described above for the preparation of an aqueous adhesive composition. Preferably, the aqueous adhesive composition of the present invention is a two-component composition.

[0096] As used herein, a "two-component" or "2K" composition is one in which at least a portion of the reactive components readily react and at least partially cure without activation from an external energy source, for example at ambient temperature (e.g., a temperature in the range of 20-25°C) or at slightly elevated temperatures (e.g., a temperature in the range of 25°C to 60°C at the time of mixing). One of ordinary skill in the art will understand that the two components of the composition are stored separately from one another and mixed immediately prior to application to the composition.

[0097] As used herein, the term "aqueous" refers to a solvent that either consists solely of water or contains predominantly water (e.g., at least 50% by weight water) in combination with a non-aqueous solvent. A non-aqueous solvent can be used in the aqueous adhesive composition of the present invention in small amounts, if desired. The amount of non-aqueous solvent can be 3% by weight or less, preferably 2% by weight or less, more preferably 1.5% by weight or less, most preferably 1% by weight or less, especially 0.5% by weight or less, based on the solids content of the aqueous adhesive composition. Examples of suitable non-aqueous solvents include, but are not limited to, toluene, acetone, methyl ethyl ketone, cyclohexane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol methyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ether, dimethylformamide, dimethyl sulfoxide, monohydric alcohols such as methanol and ethanol, and polyhydric alcohols. The aqueous adhesive composition is preferably free of non-aqueous solvents.

[0098] Furthermore, the present invention relates to an aqueous adhesive composition comprising (i) the polymer latex of the present invention as described above or the polymer latex prepared by the method of the present invention as described above, and (ii) a polyisocyanate compound.

[0099] All of the compounds and their relative amounts used in preparing the polymer latex and polymer latex of the present invention can be as described above.

[0100] According to the present invention, the aqueous adhesive composition can comprise at least 15 wt%, for example at least 17 wt%, at least 20 wt%, or at least 23 wt% of the polymer latex (i) based on the total solids content of the aqueous adhesive composition. The aqueous adhesive composition can comprise up to 50 wt%, for example up to 48 wt%, up to 45 wt%, up to 43 wt%, or up to 40 wt% of the polymer latex (i) based on the total solids content of the aqueous adhesive composition. A person skilled in the art will understand that any range between any of the explicitly disclosed lower and upper limits is disclosed herein. Thus, the aqueous adhesive composition can comprise 15-50 wt%, preferably 17-45 wt%, more preferably 20-40 wt% of the polymer latex (i) based on the total solids content of the aqueous adhesive composition.

[0101] As used herein, the term "polyisocyanate" refers to a compound having multiple isocyanate groups per molecule, for example, 2, 3, 4, 5, 6 or more isocyanate groups per molecule. Suitable polyisocyanates can be aliphatic, aromatic, or mixtures thereof. The polyisocyanate can include toluene diisocyanate, hydrogenated toluene diisocyanate, methylene diphenyl diisocyanate, hydrogenated methylene diphenyl diisocyanate, triphenylmethane triisocyanate, 1,2,4-benzene triisocyanate, polymethylene polyphenyl polyisocyanate, xylene diisocyanate, tetramethylxylylene diisocyanate, 1,6-hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, isophorone diisocyanate, and 4,4'-methylene-bis(cyclohexylisocyanate). Examples of suitable polyisocyanates that can be used in accordance with the present invention include Bayhydur and Desmodur grades of polyisocyanates available from Covestro (Germany) and Suprasec grades of polyisocyanates available from Huntsman (USA).

[0102] The aqueous adhesive composition may comprise at least 1 wt%, for example at least 2 wt%, at least 5 wt%, or at least 7 wt% of the polyisocyanate compound (ii) based on the total solids content of the aqueous adhesive composition. The aqueous adhesive composition may comprise up to 50 wt%, for example up to 48 wt%, up to 45 wt%, up to 43 wt%, or up to 40 wt% of the polyisocyanate compound (ii) based on the total solids content of the aqueous adhesive composition. A person skilled in the art will understand that any range between any of the explicitly disclosed lower and upper limits is disclosed herein. Thus, the aqueous adhesive composition may comprise 1 to 50 wt%, preferably 2 to 45 wt%, more preferably 5 to 40 wt% of the polyisocyanate compound (ii) based on the total solids content of the aqueous adhesive composition.

[0103] The aqueous adhesive composition of the present invention may further comprise polyvinyl alcohol, vinyl alcohol-ethylene copolymer, silanol modified polyvinyl alcohol, cellulose derivatives such as methyl cellulose, ethyl cellulose, hydroxycellulose and carboxycellulose, chitin, chitosan, starch, polyethylene glycol, polypropylene glycol, polyvinyl ether, gelatin, casein, cyclodextrin, and combinations thereof. Preferably, the aqueous adhesive composition of the present invention further comprises polyvinyl alcohol. As used herein, the term "polyvinyl alcohol" is generally accepted in the art as fully or partially hydrolyzed polyvinyl acetate. Polyvinyl alcohol may have a degree of saponification up to 99%. Here, the term "degree of saponification" refers to the ratio of hydroxyl groups to the total number of hydroxyl groups and carbonyloxy groups such as acetyloxy groups in polyvinyl alcohol. The degree of saponification must be understood as an average value, which means that a mixture of less hydrolyzed and more hydrolyzed polyvinyl alcohol may be used. Preferably, a degree of saponification in the range of 70-99%, more preferably 80-97% is used. Suitable examples of polyvinyl alcohol include, but are not limited to, Poval grade polyvinyl alcohol available from Kuraray Co., Ltd. (Japan).

[0104] According to the present invention, polyvinyl alcohol, vinyl alcohol-ethylene copolymer, silanol-modified polyvinyl alcohol, cellulose derivatives such as methyl cellulose, ethyl cellulose, hydroxycellulose and carboxycellulose, chitin, chitosan, starch, polyethylene glycol, polypropylene glycol, polyvinyl ether, gelatin, casein, cyclodextrin, and combinations thereof can be used in an amount of at least 3% by weight, for example at least 5% by weight, at least 7% by weight, or at least 9% by weight, based on the total solids content of the aqueous adhesive composition. Polyvinyl alcohol, vinyl alcohol-ethylene copolymer, silanol-modified polyvinyl alcohol, cellulose derivatives such as methyl cellulose, ethyl cellulose, hydroxycellulose and carboxycellulose, chitin, chitosan, starch, polyethylene glycol, polypropylene glycol, polyvinyl ether, gelatin, casein, cyclodextrin, and combinations thereof can be used in an amount of up to 60% by weight, for example up to 50% by weight, up to 45% by weight, or up to 40% by weight, based on the total solids content of the aqueous adhesive composition. One skilled in the art would understand that any range between any of the explicitly disclosed lower and upper limits is disclosed herein. Thus, polyvinyl alcohol, vinyl alcohol-ethylene copolymers, silanol modified polyvinyl alcohol, cellulose derivatives such as methyl cellulose, ethyl cellulose, hydroxycellulose and carboxycellulose, chitin, chitosan, starch, polyethylene glycol, polypropylene glycol, polyvinyl ether, gelatin, casein, cyclodextrin, and combinations thereof can be used in amounts of 3-60% by weight, preferably 5-50% by weight, more preferably 7-40% by weight, based on the total solids content of the aqueous adhesive composition.

[0105] The aqueous adhesive composition may comprise at least 3 wt%, for example at least 5 wt%, or at least 7 wt%, of polyvinyl alcohol, based on the total solids content of the aqueous adhesive composition. The aqueous adhesive composition may comprise up to 60 wt%, for example up to 50 wt%, up to 45 wt%, or up to 40 wt%, of polyvinyl alcohol, based on the total solids content of the aqueous adhesive composition. One of ordinary skill in the art will understand that any range between any of the explicitly disclosed lower and upper limits is disclosed herein. Thus, the aqueous adhesive composition may comprise 3-60 wt%, preferably 5-50 wt%, more preferably 7-40 wt%, of polyvinyl alcohol, based on the total solids content of the aqueous adhesive composition.

[0106] Optionally, the aqueous adhesive composition may further comprise a polymer latex different from that of the present invention, such as polyvinyl acetate, vinyl acetate-ethylene copolymer, polyurethane, acrylonitrile-butadiene copolymer, and combinations thereof, preferably polyvinyl acetate, vinyl acetate-ethylene copolymer, and combinations thereof. The aqueous adhesive composition may comprise up to 40% by weight, such as up to 30% by weight, up to 20% by weight, up to 10% by weight, or up to 5% by weight, of a polymer latex different from that of the present invention, preferably polyvinyl acetate, vinyl acetate-ethylene copolymer, where the weight percentage is based on the total solids content of the aqueous adhesive composition.

[0107] The aqueous adhesive composition may further include additives such as plasticizers, defoamers, thickeners, leveling agents, dispersants, colorants, water resistance additives, lubricants, pH adjusters, biocides, antioxidants, inorganic pigments, surfactants, and combinations thereof. These additives may be used in amounts ranging from 0.1 to 30% by weight, based on the total solids content of the aqueous adhesive composition.

[0108] The aqueous adhesive composition may include fillers or extenders, inorganic pigments, and combinations thereof. Suitable examples of inorganic pigments, fillers or extenders include compounds of metal oxides, hydroxides, sulfides, carbonates, sulfates, or silicates of magnesium, calcium, zinc, barium, titanium, aluminum, antimony, and lead, preferably calcium carbonate, kaolin, talc, titanium dioxide, aluminum hydroxide, silica, gypsum, baryta powder, alumina white, and satin white. The fillers or extenders, inorganic pigments, and combinations thereof may be used in an amount ranging from 30 to 60% by weight, based on the total solids content of the aqueous adhesive composition.

[0109] According to the present invention, the aqueous adhesive composition may be a two-component adhesive composition. Typically, the first component comprises the polymer latex of the present invention, and the second component comprises a polyisocyanate compound. The first component may further comprise polyvinyl alcohol, vinyl alcohol-ethylene copolymer, silanol-modified polyvinyl alcohol, cellulose derivatives such as methyl cellulose, ethyl cellulose, hydroxycellulose and carboxycellulose, chitin, chitosan, starch, polyethylene glycol, polypropylene glycol, polyvinyl ether, gelatin, casein, cyclodextrin, and combinations thereof. Preferably, the first component further comprises polyvinyl alcohol. The first component may further comprise additives, fillers or extenders, inorganic pigments, and combinations thereof.

[0110] The water-based adhesive of the present invention may be in the form of a wood adhesive. As used herein, the term "wood adhesive" refers to an adhesive for tightly bonding pieces of wood together. In particular, the water-based adhesive is in the form of D4 wood adhesive. As used herein, the term "D4 wood adhesive" refers to a wood adhesive suitable for use in interior applications with frequent long-term exposure to running or condensing water and / or exterior applications exposed to weather. According to European Standard EN204:2001, D4 wood adhesive has a strength of 4 N / mm 2 The adhesive strength is greater than 100%.

[0111] The present invention further relates to a method for preparing an aqueous adhesive composition comprising providing (i) a polymer latex of the present invention or (i) a polymer latex prepared by the method for preparing a polymer latex of the present invention, and (ii) mixing with a polyisocyanate compound.

[0112] All variations in the compounds and their relative amounts used in preparing the aqueous adhesive composition of the present invention may be as described above.

[0113] The water-based adhesive of the present invention may be in the form of a wood adhesive. Preferably, the water-based adhesive is in the form of D4 wood adhesive.

[0114] The invention will now be further described with reference to the following examples. EXAMPLES

[0115] Below, all parts and percentages are by weight unless otherwise stated.

[0116] Preparation of styrene butadiene polymer (XSBR) latex The polymer latex compositions used in the examples and comparative examples were prepared by free radical emulsion polymerization carried out in a pressure resistant stainless steel reactor connected to a cryostat allowing temperature control of the reactor jacket.

[0117] The initial charge in the reactor consisted of 66 pphm (parts by weight based on 100 parts total monomer weight) of deionized water and polystyrene seeds with an average particle size of 35 nm (seed amount for each example listed in Tables 1 and 2). After heating the initial charge to 85° C. under continuous stirring using a three-layer cross-beam stirrer, the polymerization reaction was started by starting the feed of 3.5% (w / w) sodium persulfate solution (1 pphm). The temperature was kept constant at 85° C. Two minutes after starting the persulfate feed, the monomers (amounts for each example listed in Tables 1 and 2), the chain transfer agent tert-dodecyl mercaptan, and the anionic surfactant (C 13 -C 15 An aqueous solution of alkylarylsulfonate (0.5 pphm) was added to the reactor at a constant feed rate over a period of 5 hours. Then, a post-activation feed of 0.25 pphm sodium persulfate was started to reduce residual monomer and continued for 1 hour at a batch temperature of 90°C. After complete sodium persulfate addition, the batch was held at 90°C for an additional 30 minutes with continuous stirring. The product was then cooled to ambient temperature and the pH was adjusted to 5 with 10 wt% aqueous sodium hydroxide solution, and the total solids content of the final latex was adjusted to 47.5 wt%. Finally, the latex was sieved onto a filter cloth with a mesh width of 50 μm.

[0118] The particle size of the latex was measured by dynamic light scattering according to ISO22412:2017 using a dynamic light scattering instrument Mastersizer 2000 (Malvern Panalytical, UK).

[0119] [Table 1]

[0120] [Table 2]

[0121] Preparation of wood adhesive A wood adhesive containing the polymer latex obtained above was prepared. The wood adhesive consisted of component (i) (wood adhesive compound) and hardener component (ii).

[0122] Preparation of component (i) Step 1: Preparation of polyvinyl alcohol solution: A glass beaker was placed on a magnetic stirrer and 800 mL of chilled deionized water was added to the beaker. 200 g of polyvinyl alcohol (PVA) powder (Poval PVA-CST, available from Kuraray) was slowly added to the gently stirred water and allowed to swell for 20 minutes. Upon heating to 95°C, the PVA dissolved. After holding the temperature for an additional 45 minutes, the solution was cooled to 50°C and 2 g of sodium metabisulfite was added and dissolved. The solution was filtered. The 20 wt% PVA solution was cooled to room temperature and kept overnight.

[0123] Step 2: Preparation of the wood adhesive compound (component (i)) To obtain component A, 350 g of XSBR latex, 4 g of dispersant Dispex AA4140 (available from BASF, Germany), 4 g of wetting agent Lumiten I-SC (available from BASF, Germany), 1.5 g of defoamer Foamaster 111 (available from BASF, Germany), 300 g of the PVA solution from step 1, and 250 g of 325 mesh calcium carbonate powder (ExCal 325, available from RE Carroll, USA) were mixed and adjusted to 47.5 wt. % solids with 90.5 g of water. The pH was approximately 8-9 and the Brookfield viscosity RVT was in the range of 15,000-30,000 cPoise at 20 rpm and spindle 7.

[0124] Step 3: Mixing components (i) and (ii) The final wood adhesive formulation was obtained by homogenizing 85% by weight of component (i) with 15% by weight of polymeric diphenylmethane diisocyanate (Desmodur 44V20L, commercially available from Covestro, Germany).

[0125] Pot life measurement As explained above, the wood adhesive of the present invention is a 2K system, and from the moment of mixing the two wood adhesive components (i) and (ii), hardening starts. As hardening progresses, the viscosity of the wood adhesive gradually increases over time. Beyond a certain limit, the viscosity no longer allows for proper application of the wood adhesive. A critical viscosity threshold is defined at a value of 150,000 cPoise. For practical reasons (e.g. unintended line stops), a pot life of 60 minutes is a minimum requirement in terms of laminated timber production, especially in terms of automated processing using robotic dispensers. Any value above 60 minutes is beneficial.

[0126] One minute after mixing components (i) and (ii), the Brookfield viscosity RVT was measured at 20 rpm, spindle 7 for wood adhesive. The viscosity gradually increased with time. The viscosity increase was monitored at 5 minute intervals until a threshold value of 150,000 cPoise was reached. The result was taken as the time from the first measurement 1 minute after mixing to the first result exceeding 150,000 cPoise.

[0127] Measurement of wood bond strength The test was carried out according to the European standard EN205:2003, which describes the test of adhesives to evaluate their resistance to hot and cold water. Here, bonds with thin bond lines were evaluated. Several panels of beech wood with dimensions according to EN205:2003 were glued together with wood adhesive, pressed tightly, conditioned for 7 days in a standard atmosphere (23±2°C and 50±5% relative humidity) and finally cut to obtain specimens suitable for tensile shear testing. Ten specimens with each adhesive were prepared and the average value of the valid results was calculated. Before measuring the bond strength with the tensile shear tester, the wood specimens were subjected to conditions of durability category D4 according to the European standard EN204:2001. The wood specimens were treated for 7 days in a standard atmosphere (23±2°C and 50±5% relative humidity), followed by 6 hours in boiling water and then 2 hours in water at 20±2°C.

[0128] The specimens were tested on a tensile testing machine (zwickiLine Z5.0TS available from ZwickRoell, Germany) capable of reaching a constant traverse speed at a rate of 50 mm / min.

[0129] According to the European standard EN204:2001, the minimum adhesive strength for D4 durability category is 4N / mm 2 It's super.

[0130] The pot life and wood bond strength results of the wood adhesives containing the XSBR latexes of Examples 1-12 are shown in Tables 3 and 4.

[0131] [Table 3]

[0132] [Table 4]

Claims

1. Polymer latex for adhesive compositions obtained by free radical emulsion polymerization of a mixture of ethylenically unsaturated monomers: Here, the mixture of ethylenically unsaturated monomers is (a) Vinyl aromatic monomers, (b) Conjugated diene monomers, and (c) comprising an ethylenically unsaturated monomer having an acidic functional group and / or a hydroxyl functional group, The weight ratio of vinyl aromatic monomer (a) to conjugated diene monomer (b) is in the range of 1.60 to 2.

30. The polymer latex has a median particle size of at least 220 nm.

2. The polymer latex according to claim 1, wherein the total of the vinyl aromatic monomer (a) and the conjugated diene monomer (b) is in the range of 85.0 to 99.0% by weight, based on the total weight of the monomers in the monomer mixture.

3. The polymer latex according to claim 1 or 2, wherein the mixture of ethylenically unsaturated monomers comprises (a) 40 to 80% by weight of vinyl aromatic monomers based on the total weight of monomers in the monomer mixture.

4. The polymer latex according to claim 1 or 2, wherein the mixture of ethylenically unsaturated monomers comprises (b) 15 to 50% by weight of conjugated diene monomers based on the total weight of monomers in the monomer mixture.

5. The polymer latex according to claim 1 or 2, wherein the mixture of ethylenically unsaturated monomers comprises (c) 0.2 to 6.0% by weight of ethylenically unsaturated monomers having acidic and / or hydroxyl functional groups, based on the total weight of monomers in the monomer mixture.

6. The weight ratio of vinyl aromatic monomer (a) to conjugated diene monomer (b) is in the range of 1.70 to 2.10, and / or The polymer latex has a median particle size of at least 230 nm, as described in claim 1 or 2.

7. The polymer latex according to claim 1 or 2, comprising a mixture of ethylenically unsaturated monomers, comprising 0.05 to 3.0% by weight of a chain transfer agent, where the weight percentage is based on the total amount of monomers in the monomer mixture.

8. The polymer latex according to claim 1 or 2, wherein the mixture of ethylenically unsaturated monomers comprises (d) 0 to 20% by weight of ethylenically unsaturated monomers different from (a) to (c), based on the total weight of monomers in the monomer mixture.

9. A method for preparing polymer latex for adhesives, A method comprising polymerizing a mixture of ethylenically unsaturated monomers by free radical emulsion polymerization: Here, the mixture of ethylenically unsaturated monomers is (a) Vinyl aromatic monomers, (b) Conjugated diene monomers, and (c) comprising an ethylenically unsaturated monomer having an acidic functional group and / or a hydroxyl functional group, The weight ratio of vinyl aromatic monomer (a) to conjugated diene monomer (b) is in the range of 1.60 to 2.

30. The polymer latex has a median particle size of at least 220 nm.

10. The weight ratio of vinyl aromatic monomer (a) to conjugated diene monomer (b) is in the range of 1.70 to 2.10, and / or The method according to claim 9, wherein the total of the vinyl aromatic monomer (a) and the conjugated diene monomer (b) is in the range of 85.0 to 99.0% by weight, based on the total weight of the monomers in the monomer mixture.

11. The method according to claim 9 or 10, wherein the mixture of ethylenically unsaturated monomers comprises at least one, two or more, or all of (a), (b), and (c) below: (a) 40 to 80% by weight of vinyl aromatic monomer; (b) 15 to 50% by weight of conjugated diene monomer; and (c) 0.5 to 5.0% by weight of an ethylenically unsaturated monomer having an acidic functional group and / or a hydroxyl functional group; Weight percentage is based on the total weight of monomers in the monomer mixture.

12. The method according to claim 9 or 10, wherein the mixture of ethylenically unsaturated monomers comprises 0.05 to 3.0% by weight of a chain transfer agent, where the weight percentage is based on the total amount of monomers in the monomer mixture.

13. The method according to claim 9 or 10, wherein the polymer latex has a median particle size of at least 230 nm.

14. Use of the polymer latex described in claim 1 or 2 or a polymer latex prepared by the method described in claim 9 or 10 for the preparation of an aqueous adhesive composition.

15. (i) a polymer latex according to claim 1 or 2 or a polymer latex prepared by the method described in claim 9 or 10, and (ii) a polyisocyanate compound, comprising an aqueous adhesive composition.

16. (ii) Polyisocyanate compounds include toluene diisocyanate, hydrogenated toluene diisocyanate, methylenediphenyl diisocyanate, hydrogenated methylenediphenyl diisocyanate, triphenylmethane triisocyanate, 1,2,4-benzene triisocyanate, polymethylene polyphenyl polyisocyanate, xylene diisocyanate, tetramethylxylylene diisocyanate, 1,6-hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, isophorone diisocyanate, and 4,4'-methylene-bis(cyclohexyl isocyanate), and / or Furthermore, the aqueous adhesive composition according to claim 15 comprises polyvinyl alcohol, vinyl alcohol-ethylene copolymer, silanol-modified polyvinyl alcohol, cellulose derivatives, chitin, chitosan, starch, polyethylene glycol, polypropylene glycol, polyvinyl ether, gelatin, casein, cyclodextrin, and combinations thereof.

17. The aqueous adhesive composition according to claim 15, wherein the first component comprises a polymer latex and optionally polyvinyl alcohol, vinyl alcohol-ethylene copolymer, silanol-modified polyvinyl alcohol, cellulose derivative, chitin, chitosan, starch, polyethylene glycol, polypropylene glycol, polyvinyl ether, gelatin, casein, cyclodextrin, and combinations thereof, and the second component comprises a polyisocyanate compound.

18. The aqueous adhesive composition according to claim 15, comprising 1 to 50% by weight of a polyisocyanate compound (ii) based on the total solids content of the aqueous adhesive composition.

19. The aqueous adhesive composition according to claim 15, which is in the form of a wood adhesive.

20. A method for preparing an aqueous adhesive composition, (i) providing a polymer latex according to claim 1 or 2 or a polymer latex prepared by the method described in claim 9 or 10, and (ii) a method comprising mixing with a polyisocyanate compound.