JP4792227B2 - Aqueous adhesive dispersion - Google Patents

Description

  The present invention relates to an aqueous adhesive dispersion.

  Conventionally, as a nonwoven fabric filter used in an air cleaner or the like, a nonwoven fabric using polyester fibers mainly made of polyethylene terephthalate has been used. However, since it is difficult to keep the shape of the nonwoven fabric made of polyester fiber as it is when folded, the nonwoven fabric is produced by adding a binder made of a polymer compound.

  As such a nonwoven fabric binder, a polyacrylate binder is widely used. Such polyacrylate binders are often used together with thermosetting resins such as urea resins and phenol resins. However, these binders may generate formaldehyde when heated, making them unsuitable for use in clothing and sanitary materials. Therefore, as a binder that does not generate formaldehyde, an acrylate monomer or a styrene monomer is dispersed using a water-soluble polymer such as polyvinyl alcohol, and emulsion polymerization is performed. Patent Document 1 discloses an emulsion obtained by graft polymerization on a part.

JP 2001-151975 A

  However, with such a binder, formaldehyde is not generated, but shape retention is insufficient when the nonwoven fabric is bent and then subjected to a heat history of 80 ° C. or higher. This is thought to be due to insufficient rigidity. As a highly rigid binder, there is an example in which a polymer containing styrene or the like as a main component is used, but discoloration during heating sometimes becomes a problem.

  Accordingly, an object of the present invention is to produce a binder that does not produce formaldehyde and that can be sufficiently obtained in shape retention with little discoloration when being folded using a nonwoven fabric.

  The present invention relates to a glass transition temperature obtained by polymerizing a monomer mixture containing at least a polymerizable monomer having a carboxyl group, a (meth) acrylic monomer having no carboxyl group, and a crosslinkable monomer. An aqueous adhesive dispersion containing a (meth) acrylic polymer (A) having a temperature of 40 ° C. or higher and lower than 80 ° C. and a water-soluble polyester (C) having a glass transition temperature of 40 ° C. or higher and 100 ° C. or lower. By using it, the above-mentioned problems have been solved.

  By using the aqueous adhesive dispersion according to the present invention as a binder for nonwoven fabric, it is possible to improve the adhesion between the binder and the base material, and to ensure sufficient shape retention when the resulting nonwoven fabric is bent. Become.

The present invention will be described in detail below.
This invention is an aqueous adhesive dispersion containing a predetermined (meth) acrylic polymer (A) and a water-soluble polyester (C). “(Meth) acryl” means “methacryl” or “acryl”.

  First, the (meth) acrylic polymer (A) will be described. This (meth) acrylic polymer (A) is a monomer mixture containing at least a polymerizable monomer having a carboxyl group, a (meth) acrylic monomer having no carboxyl group, and a crosslinkable monomer. It is a polymer having a specific glass transition temperature obtained by polymerizing.

  Examples of the polymerizable monomer having a carboxyl group include acrylic acid, methacrylic acid, itaconic acid, maleic acid, and maleic anhydride.

  Examples of the (meth) acrylic monomer having no carboxyl group include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, (meth ) Butyl acrylate, isobutyl (meth) acrylate, (meth) acrylic acid (sec-butyl), (meth) acrylic acid (tert-butyl), pentyl (meth) acrylate, hexyl (meth) acrylate, (meth ) Heptyl acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, etc. (Meth) acrylic acid alkyl ester containing an alkyl group having 1 to 12 carbon atoms, or (meth) a Acrylic acid hydroxymethyl, like hydroxyethyl (meth) acrylate.

  The above-mentioned crosslinkable monomer means a monomer having a functional group capable of forming a crosslink by reacting with the above polymerizable monomer having a carboxyl group. For example, (meth) acrylic Examples include epoxy group-containing (meth) acrylic monomers such as glycidyl acid.

  As said monomer mixture, it is preferable to contain 50 weight% or more of (meth) acrylic-acid alkylester containing a C1-C12 alkyl group, and it is more preferable that it is 80 weight% or more. This is because if it is less than 50% by weight, the characteristics of other monomers to be copolymerized are strong and it becomes difficult to obtain desired physical properties. As an upper limit, it is preferable that it is 98.9 weight% or less, and it is more preferable that it is 98 weight% or less. If it exceeds 98.9% by weight, the monomer content contributing to the crosslinking reaction will be low, and sufficient crosslinking may not be obtained.

  In addition, the content of the polymerizable monomer having a carboxyl group contained in the monomer mixture is preferably 0.1% by weight or more, more preferably 0.5% by weight or more. preferable. If it is less than 0.1% by weight, the number of cross-linking points may be reduced and rigidity may be insufficient. The upper limit of this content is preferably 5% by weight, and more preferably 3% by weight or less. If it exceeds 5% by weight, the stability during emulsion polymerization tends to be insufficient. As the polymerizable monomer having a carboxyl group, acrylic acid is more preferable.

  Furthermore, the content of the crosslinkable monomer is preferably 1% by weight or more, and more preferably 2% by weight or more based on the monomer mixture. This is because if the crosslinkable monomer is less than 1% by weight, there is a high possibility of insufficient crosslinking and insufficient rigidity. Further, this content is preferably 5% by weight or less, and more preferably 4.5% by weight or less. If it exceeds 5% by weight, the crosslinking tends to proceed excessively, and the storage stability of the resulting dispersion containing the (meth) acrylic polymer (A) is likely to deteriorate.

  Moreover, as the monomer mixture, in addition to these monomers, aromatic vinyl compounds such as styrene and α-methylstyrene, polymerizable nitriles such as acrylonitrile, etc., as long as the effects of the present invention are not impaired. Vinyl esters such as vinyl acetate may be used.

  Next, the method for obtaining the (meth) acrylic polymer from the monomer mixture is not particularly limited, and examples thereof include sodium persulfate and anhydrous sodium bisulfite in the presence of an anionic and nonionic emulsifier. An emulsion polymerization method using a water-soluble polymerization initiator is preferably used.

  In this invention, the (meth) acrylic polymer (A) obtained by polymerizing the monomer mixture must have a glass transition temperature of 40 ° C. or higher, and 50 ° C. or higher. Preferably there is. If the glass transition temperature is less than 40 ° C., the rigidity is insufficient and the resulting molded article may be deformed by heating after molding. On the other hand, the glass transition temperature of the (meth) acrylic polymer needs to be less than 80 ° C., and is preferably 70 ° C. or less. When it is 80 ° C. or higher, the film forming property when used as a binder is insufficient, and a uniform binder effect may not be obtained. The glass transition temperature can be adjusted by the type of monomer used in the monomer mixture, the mixing ratio, the polymerization temperature, and the like.

  Next, water-soluble polyester (C) is demonstrated. The water-soluble polyester (C) refers to a polyester that can be dissolved or uniformly dispersed in water, and gives a uniform aqueous solution or a uniform dispersion at a solid concentration of 25% by weight.

  The water-soluble polyester (C) comprises a polyhydric alcohol (d) and at least one polybasic acid compound (e) selected from the group consisting of a polycarboxylic acid, an acid anhydride thereof and a lower alkyl ester thereof. The mixture further includes a hydrophilic component (f) having a hydrophilic group, an alkyl group in the above (meth) acrylic acid alkyl ester, a hydroxyl group of the polyhydric alcohol (d), and / or the polybasic acid compound. It is obtained by adding a compound (g) having one functional group capable of reacting with the carboxyl group of (e), etc., as necessary, and copolymerizing (copolyesterification). However, when a trihydric or higher polyhydric alcohol, a polyvalent carboxylic acid derivative and a polyvalent epoxy compound are used, the trihydric or higher compound is preferably used in an amount of 40 mol% or less in all constituent monomers. When the amount exceeds 40 mol%, the three-dimensional crosslinking reaction proceeds in the resin, making it difficult to disperse in an aqueous medium.

  Here, the polyhydric alcohol (d) constituting the water-soluble polyester (C) refers to a compound having two or more hydroxyl groups in the molecule, for example, ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, diester. Propylene glycol, polypropylene glycol, 1,4-butanediol, 1,3-propanediol, neopentyl glycol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, 1,6-hexanediol, 1,6- Cyclohexanedimethanol, p-xylylene glycol, bisphenol A, hydrogenated bisphenol A, bisphenol A alkylene oxide adduct, glycerin, trimethylolethane, trimethylolpropane, trishydroxyethyl isocyanur Over DOO, pentaerythritol, dimethylol propionic acid and dimethylol butanoic acid. Performs copolymerization using one or more of these. Such water-soluble polyester (C) is, for example, “Plus Coat Z-446 (trade name)” manufactured by Kyoyo Chemical Industry Co., Ltd. or “ES-2200 (trade name)” manufactured by Dainippon Ink & Chemicals, Inc. Available as

  Examples of the polybasic acid compound (e) include compounds having two or more carboxyl groups in the molecule or acid anhydrides thereof, and polyester precursor compounds such as lower alkyl esters such as methyl esters. For example, adipic acid, succinic acid, succinic anhydride, alkyl succinic acid having 8 to 20 carbon atoms, alkyl succinic anhydride, alkenyl succinic acid, alkenyl succinic anhydride, sebacic acid, dodecanedioic acid, itaconic acid, maleic acid, maleic acid Aliphatic dicarboxylic acids such as acid, maleic anhydride, 1,4-cyclohexanedicarboxylic acid and dimer acid and their anhydrides, phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, trimellitic acid, trimellitic anhydride, cyanur Acid, pyromellitic acid, pyromellitic anhydride, rosin acid, 2,6-naphthalenedicarbo Acid, 4,4'-biphenyl dicarboxylic acid, aromatic dicarboxylic acids such as phenylindanedicarboxylic acid or its anhydride and the like, perform copolymerization using one or more of these.

  Examples of the hydrophilic component (f) having a hydrophilic group include compounds having a sulfonic group such as an alkali metal sulfonate compound, polyethylene glycol, and the like. Examples of the sulfonic acid alkali metal salt compounds include sodium 5-sulfoisophthalate, 5-ammonium sulfoisophthalic acid, sodium 4-sulfoisophthalate, 4-methylammonium sulfoisophthalic acid, sodium 2-sulfoterephthalate, 5-sulfoisophthalic acid potassium, 4-sulfoisophthalic acid potassium, 2-sulfoterephthalic acid potassium, sodium sulfosuccinate, sulfonic acid sodium salt-containing bisphenol A, sulfonic acid sodium salt-containing bisphenol A alkylene oxide adduct, sulfonic acid potassium base-containing Examples thereof include hydroquinone alkylene oxide adducts.

  Next, as the compound (g) having one functional group that reacts with the alkyl group, the hydroxyl group of the polyhydric alcohol (d), and / or the carboxyl group of the polybasic acid compound (e), for example, And compounds having a functional group such as an alkyl group and a hydroxyl group, a carboxyl group, an epoxy group, an isocyanate group, and an amino group. Among these, a compound having one alkyl group and one epoxy group is preferred. In addition, the alkyl group of the compound (g) is preferably an alkyl group having 4 to 23 carbon atoms in order to adjust the balance between hydrophilicity and hydrophobicity, and the alkyl group may have a branched structure. Further, the above alkyl group may have a substituent.

  In addition to these, when the polyester resin is obtained by copolymerization, a monohydric alcohol or a monovalent carboxylic acid derivative can be used in combination in order to control the number of terminal functional groups.

  Such a polyester resin is neutralized by adding a neutralizing agent as necessary, and dispersed or dissolved in an aqueous medium to form a dispersion or a uniform solution, which is used as the water-soluble polyester (C).

  By mixing the water-soluble polyester (C) with the (meth) acrylic polymer (A), the adhesion to the nonwoven fabric is improved, and the shape retention during bending is further improved.

  In order to make the aqueous adhesive dispersion according to the present invention contain the (meth) acrylic polymer (A) and the water-soluble polyester (C), the (meth) acrylic polymer (A ) And the water-soluble polyester (C), or by mixing the water-soluble polyester (C) with the monomer mixture in advance and then polymerizing the monomer mixture to produce the (meth) There is a method of obtaining the acrylic polymer (A), and a method of performing polymerization after mixing in advance is more preferable. By mixing the water-soluble polyester (C) before polymerization, the uniformity of the aqueous adhesive dispersion obtained can be improved.

  The mixing ratio of the (meth) acrylic polymer (A) to the water-soluble polyester (C) is 1 weight of the water-soluble polyester (C) with respect to the (meth) acrylic polymer (A). It is preferable to use it so that it may become% or more (solid content ratio), and it is more preferable that it is 3 weight% or more. If the amount is less than 1% by weight, the improvement effect by addition cannot be sufficiently obtained. A preferable upper limit is 15% by weight, and more preferably 10% by weight or less. Even if it is used in excess of 15% by weight, there is no increase in the effect commensurate with the increase in the amount added, which is not economical.

  In addition to the (meth) acrylic polymer (A) and the water-soluble polyester (C), the aqueous adhesive dispersion according to the present invention includes natural rubber and synthetic rubber as long as the effects of the present invention are not impaired. Or rubbers such as ethylene-vinyl acetate copolymer, polyurethane and the like. Moreover, in order to improve the adhesive strength of this aqueous adhesive dispersion and the rigidity of the molded article obtained, it is preferable to contain a metal crosslinking agent (B).

  Said metal crosslinking agent (B) means the metal compound which can bridge | crosslink the carboxyl group in the said (meth) acrylic-type polymer (A), for example, zirconium carbonate ammonium, zirconium carbonate potassium, zirconium fluoride. Zirconium compounds such as hydroacid, zirconium zirconium fluoride, zirconium zirconium fluoride, sodium zirconium fluoride, zirconium acetyl acetate, zirconium butoxide 1-butanol are preferably used. Of these, ammonium zirconium carbonate is particularly preferred because it is easily available and has a high crosslinking effect.

  By adding the above metal cross-linking agent (B), the aqueous adhesive dispersion according to the present invention increases the adhesive force, and retains the shape when a product such as a nonwoven fabric produced using the same is bent. Can be further enhanced.

  A preferable blending ratio when adding the metal crosslinking agent (B) to the aqueous adhesive dispersion according to the present invention is the metal crosslinking agent (B) with respect to the (meth) acrylic polymer (A). (Solid content) is preferably used at a blending ratio of 0.1% by weight or more, and more preferably 0.3% by weight or more. If it is less than 0.1% by weight, the crosslinkability may be insufficient. Moreover, the compounding ratio with which the ratio of the said metal crosslinking agent (B) (solid content) with respect to the said (meth) acrylic-type copolymer (A) is 3 weight% or less is preferable, and it is more preferable that it is 2 weight% or less. . Even if it is used in excess of 3% by weight, an increase in effect commensurate with the increase in the amount added cannot be obtained, which is not economical.

  The aqueous adhesive dispersion according to the present invention is suitably used, for example, when a nonwoven fabric substrate is impregnated and bonded by a known method to produce a nonwoven fabric. The nonwoven fabric produced using the aqueous adhesive dispersion according to the present invention has high rigidity and shape retention at the time of bending, and is preferable, for example, when used for a filter for an air purifier, because the durability is improved. .

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist. First, the chemicals and materials to be used will be described, and then the measurement method will be described.

((Meth) acrylic monomer without carboxyl group)
・ Methyl methacrylate: manufactured by Mitsubishi Chemical Corporation (hereinafter referred to as “MMA”)
・ Butyl acrylate: Mitsubishi Chemical Corporation (hereinafter referred to as “BA”)
・ Ethyl acrylate: Mitsubishi Chemical Corporation (hereinafter referred to as “EA”)
(Crosslinkable monomer)
・ Glycidyl methacrylate: Mitsubishi Gas Chemical Co., Ltd. (hereinafter referred to as “GMA”)
(Acrylic monomer containing carboxyl group)
・ Acrylic acid ... Mitsubishi Chemical Co., Ltd. (hereinafter referred to as “AA”, solid content concentration 80% by weight)

(Water-soluble polyester (C))
・ Plus Coat Z-446 ...... Made by Kyoyo Chemical Industry Co., Ltd., solid content concentration: 25% by weight (aqueous solution)
(Surfactant)
Neoperex G-65: Kao Corporation: sodium dodecylbenzenesulfonate (solid content concentration: 65% by weight, indicated as “G-65” in the table)
-Emulgen 1118S-70 ... Kao Co., Ltd. product: polyoxyethylene alkyl ether (solid content concentration: 70 weight%, described as "S-70" in the table)

(Polymerization initiator)
-Sodium persulfate: Wako Pure Chemical Industries, Ltd .: Reagent grade (hereinafter referred to as "NaPS")
Anhydrous sodium bisulfite: Wako Pure Chemical Industries, Ltd .: Reagent grade 1 (hereinafter referred to as “SBS”)
(Metal cross-linking agent (B))
-Zirconium ammonium carbonate aqueous solution: Nippon Light Metal Co., Ltd .: Baycoat 20 (solid content 40 wt%)

(Nonwoven fabric substrate)
・ Nonwoven web: made of polyethylene terephthalate

(Tensile strength measurement method)
A 1.5 cm × 8 cm test piece is cut out from the nonwoven fabric obtained by impregnating the nonwoven web with each aqueous adhesive dispersion and drying. Hold both ends of the test piece with a jig (chuck) of a tensile tester so that the length between chucks is 5 cm, and perform a tensile test at a tensile speed of 100 mm / min. Strength. The value measured in an atmosphere of 23 ° C. and 50% RH is the normal tensile strength, and the value measured immediately after the test piece is immersed in water at 23 ° C. for 1 hour is the water tensile strength.

(Glass transition temperature measurement method)
About the membrane | film | coat obtained by drying each (meth) acrylic-type polymer (A) at 80 degreeC for 24 hours, it measured using the differential scanning calorimeter (Seiko Electronics Co., Ltd. product, DSC220C).

(Bending softness measurement method)
(See JIS L 1096 8.19.2, Method B (Slide Method))
A test piece of 2.5 cm × 10 cm is cut out from a nonwoven fabric obtained by impregnating a nonwoven web with each aqueous adhesive dispersion and drying. One end of the test piece is held horizontally by a jig. This is held for 30 minutes under the condition of 65 ° C., and the distance at which the end opposite to the side on which the test piece is carried hangs down is measured to obtain the amount of sagging. The greater the sagging amount, the higher the flexibility, and the smaller the sagging amount, the higher the rigidity.

Example 1
First, in order to produce the (meth) acrylic polymer (A), 40 parts by weight of water and a surfactant (Neoperex G-65: 1 part by weight (solid) and Emulgen 1118S-70: 1.43 parts by weight) (Solid)) and a monomer mixture was prepared. The composition ratio is shown in Table 1. The composition of the monomer mixture is a weight ratio of pure product (100%) weight. In addition, unless otherwise specified, the following use amounts mean parts by weight of pure products.

  On the other hand, in a reaction vessel equipped with a stirrer, a reflux condenser, a thermometer and a dropping funnel, 5 parts by weight (solid content) of water-soluble polyester (C) and 42 parts by weight of water are placed, and the temperature is raised to 70 ° C. did. Next, 0.2 parts by weight of NaPS as a polymerization initiator and 0.05 parts by weight of SBS are added, the temperature is set to 75 ° C., and the previously prepared monomer mixture is continuously dropped over 4 hours. Then, a polymerization reaction was performed to obtain an aqueous adhesive dispersion in which the mixing ratio of the water-soluble polyester (C) to the (meth) acrylic polymer (A) was 5% by weight. The glass transition temperature Tg of the (meth) acrylic polymer (A) in this aqueous adhesive dispersion was 60 ° C.

  The aqueous adhesive dispersion was used as a binder, impregnated into a nonwoven web mainly composed of polyethylene terephthalate, drained, and dried at 140 ° C. for 4 minutes to obtain a nonwoven fabric. The component weight ratio (Fiber / Binder, abbreviated as “F / B” in the table) of the non-woven web after drying and the two-component adhesive composition as a binder was 50/50. Table 1 shows the results of measuring the tensile strength and the bending resistance of the obtained nonwoven fabric.

(Example 2)
10 parts by weight of the water-soluble polyester (C) to be added and 36 parts by weight of water, the mixing ratio of the water-soluble polyester (C) to the (meth) acrylic polymer (A) in the resulting aqueous adhesive dispersion is 10 A water-based adhesive dispersion was obtained by the same procedure as in Example 1 except that the amount was changed to% by weight. The results are shown in Table 1.

(Comparative Example 1)
Except not using water-soluble polyester (C), the dispersion liquid was obtained by the procedure similar to Example 1, and the nonwoven fabric was obtained similarly and measured. The results are shown in Table 1.

(Example 3)
With respect to the (meth) acrylic polymer (A) of Example 1, an aqueous zirconium ammonium carbonate solution as the metal cross-linking agent (B) is (A) / (B) = 100/1 in terms of solid content weight ratio. Other than that, a nonwoven fabric was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1.

(result)
In Examples 1 and 2, the normal tensile strength was improved as compared with the comparative example. Moreover, the value of bending resistance decreased and the rigidity improved. In Example 3 to which the metal crosslinking agent (B) was added, the tensile strength was slightly reduced, but the rigidity was greatly improved.

Claims (5)

Obtained by polymerizing a monomer mixture containing at least a polymerizable monomer having a carboxyl group, a (meth) acrylic monomer having no carboxyl group , and an epoxy group-containing (meth) acrylic monomer , With respect to the (meth) acrylic polymer (A) having a glass transition temperature of 40 ° C. or higher and less than 80 ° C. comprising an amount of the metal crosslinking agent (B), and glass transition temperature of 40 ° C. or higher, containing 100 ° C. or less is water-soluble polyester (C), an aqueous nonwoven binder. The binder for aqueous nonwoven fabrics according to claim 1, wherein the amount of the polymerizable monomer having a carboxyl group in the monomer mixture is 0.1 wt% or more and 5 wt% or less. Of the above monomer mixture, 50 wt% or more and 98.9 wt% or less of the monomer is at least one of (meth) acrylic acid alkyl ester having an alkyl group having 1 to 12 carbon atoms, Item 3. A binder for aqueous nonwoven fabric according to Item 1 or 2. The content of the epoxy group-containing (meth) acrylic monomer in the monomer mixture in the (meth) acrylic polymer (A) is 1 wt% or more and 5 wt% or less. The binder for aqueous nonwoven fabrics in any one of 1-3 . The metal cross-linking agent (B) is a zirconium compound, water-based nonwoven binders according to claim 4.