JP5198949B2 - Aqueous adhesive composition - Google Patents

Description

  The present invention relates to an aqueous pressure-sensitive adhesive composition, and more particularly, to an aqueous pressure-sensitive adhesive composition comprising a composite resin of urethane and a polymer of a polymerizable monomer.

  Urethane-based pressure-sensitive adhesives are useful as fine pressure-sensitive adhesives. Conventionally, urethane-based pressure-sensitive adhesives are solvent-based, and there has been a demand for solvent-free from the viewpoints of safety in the working environment and response to the environment.

  In contrast, water-based urethane adhesives have been developed. However, the urethane-based pressure-sensitive adhesive is slightly tacky and it is difficult to impart tackiness (initial adhesiveness) due to tack. On the other hand, it is conceivable to reduce the molecular weight in order to develop tackiness, but in this case, the cohesive force tends to be insufficient. As a method for improving the cohesive force, a method using a crosslinking agent in combination can be mentioned.

  However, when this cross-linking agent is used in combination, it becomes a two-component blended pressure-sensitive adhesive, and handling becomes complicated. For this reason, there is a need for a one-component solution with the above-described characteristics. Furthermore, as a defect of the urethane resin, there is a problem that the weather resistance is not sufficient, but this improvement is also demanded.

  On the other hand, solvent-based acrylic adhesives have been the mainstream in the past. However, it is difficult to obtain a high-polymerized polymer with cohesive strength due to the above-mentioned problems such as safety and environment, Therefore, there is a need to eliminate the use of solvents.

  In contrast, water-based acrylic pressure-sensitive adhesives have been developed. As compared with the solvent type, a polymer having a high degree of polymerization is obtained, and the cohesive force is sufficient. In addition, tackiness can be imparted. However, since an emulsifier is used to emulsify in water, water resistance and the like are often insufficient. In addition, it is difficult for the water-based acrylic pressure-sensitive adhesive to exhibit both fine adhesion and adhesion to various substrates.

  On the other hand, a pressure-sensitive adhesive composition using a mixed resin obtained by mixing an aqueous polyurethane and an acrylic emulsion and having a high molecular weight and improved water resistance and substrate adhesion is known (Patent Document 1).

  However, the aqueous polyurethane and acrylic emulsion constituting the mixed resin are not very compatible with each other, and therefore phase separation is likely to occur. For this reason, there exists a possibility that the transparency of a coating film may fall. In addition, water resistance tends to be insufficient due to the contribution of the emulsifier used in the acrylic emulsion.

  By the way, a composite resin in which a urethane resin and an acrylic resin are combined in a particle by combining an aqueous polyurethane and a vinyl polymer without using an emulsifier is known (Patent Document 2). Since this composite resin is a composite of both resins, it is possible to suppress a decrease in water resistance due to the emulsifier without causing phase separation, and to improve the weather resistance, which was a defect of the urethane resin.

Japanese Patent Laying-Open No. 2005-089666 JP 2000-328031 A

  However, in the invention described in Patent Document 1, the cohesive force is high and the adhesive residue is good, but inadequate in terms of adhesion to an adherend such as tackiness due to tack. There is. Further, in the invention described in Patent Document 2, a cross-linking agent is used to obtain a cohesive force, so that it is a two-component system, and the handling complexity remains.

  Accordingly, the present invention is a one-component water-based pressure-sensitive adhesive that has slight adhesiveness, has adhesion to an adherend such as tackiness, and has cohesiveness, water resistance, and weather resistance. The purpose is to obtain.

  In the aqueous dispersion containing a urethane prepolymer (A) obtained by reacting a chain aliphatic polyvalent isocyanate compound and a diol component, and a polymerizable monomer (B), A composition obtained by polymerizing the component (B), wherein the acid value of the component (A) is 25 to 70 mg KOH / g, and the glass transition of the polymer obtained by polymerizing the component (B) The said subject was solved by using the aqueous adhesive composition whose temperature is -10 degrees C or less.

Since the present invention uses a composite resin obtained by polymerizing a specific component (A) and component (B), the resulting aqueous pressure-sensitive adhesive composition has slight tackiness, cohesion, water resistance, and weather resistance. It can be used as a one-component pressure sensitive adhesive.
Moreover, since the acid value of (A) component which comprises the aqueous adhesive composition concerning this invention is made into a predetermined range, the adhesive force with adherends, such as adhesiveness by a tack, can be improved.

The present invention will be described in detail below.
The aqueous pressure-sensitive adhesive composition according to the present invention comprises a specific urethane prepolymer (referred to as “component (A)” in this specification) and a polymerizable monomer (referred to as “component (B)” in this specification). The composition obtained by polymerizing the component (B) in the aqueous dispersion.

[(A) component]
The urethane prepolymer as the component (A) is a prepolymer obtained by reacting a chain aliphatic polyvalent isocyanate compound with a diol component.

  The chain aliphatic polyvalent isocyanate compound refers to a linear and aliphatic polyvalent isocyanate compound, and specific examples include hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, or a mixture thereof. By using these chain aliphatic polyvalent isocyanates, the hard segment part contained in the urethane composition can be made flexible.

  The diol component refers to a compound having at least two hydroxyl groups as functional groups, and generally known diols are used. Examples of the diol include polyether polyols, carboxyl group-containing diols, and other diols, and it is preferable to include polyether polyols and carboxyl group-containing diols as essential components. By using polyether polyol, the produced | generated film | membrane becomes flexible and can improve the adhesiveness to a base material. Further, by using a carboxyl group-containing diol, a polar group is introduced, and in particular, adhesion to a metal is improved. In addition, it is preferable to use a silicon-modified polyol obtained by reacting polyethylene glycol with siloxanes such as dimethyldimethoxysilane because water repellency, abrasion resistance, and / or slip properties are improved. Furthermore, the urethane prepolymer (component (A)) itself can be given a role as a dispersant by neutralizing at least a part of this carboxyl group after urethane polymerization. Without using, it becomes possible to disperse the component (A) in the hydrophilic medium described later.

  Examples of the polyether polyol include polyethylene glycol, polypropylene glycol, polytetramethylene glycol and the like.

  The polyether polyol has a number average molecular weight of preferably 2500 or less, and preferably 1000 or less. When it is larger than 2500, the urethane prepolymer has a high viscosity, and the dispersibility in water may decrease. On the other hand, the lower limit of the number average molecular weight is preferably 300, more preferably 500. If it is less than 300, the tackiness that the polyurethane segment should exhibit may be insufficient. In addition, this number average molecular weight is obtained by esterification using phthalic anhydride (pyridine solution) and titration method using sodium hydroxide solution of excess phthalic anhydride in accordance with JIS-K-1557. It can be calculated by measuring (OHV).

  Examples of the carboxyl group-containing diol include dimethylol alkanoic acids such as dimethylolpropionic acid and dimethylolbutanoic acid.

  Further, examples of the other diols include ethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, and 3-methyl-1 Comparison of, 5-pentanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, trimethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, cyclohexanedimethanol, methylpentanediol adipate, etc. Low molecular weight diols, polyester diols, polyester ether diols, polymer diols such as polycarbonate diols, and silicone-modified diols such as alcohol-modified silicone oils Le, and the like, may be used those of one or more.

  The content of the polyether polyol in the total diol component is preferably 60% by weight or more, and more preferably 80% by weight or more. If it is less than 60% by weight, the tackiness may be insufficient. On the other hand, the upper limit of the content is preferably 95% by weight. When the amount is more than 95% by weight, the content of the carboxyl group-containing diol is relatively decreased, and the dispersibility in water tends to be insufficient.

  The acid value of the obtained component (A) is 25 mgKOH / g or more. When it is less than 25 mgKOH / g, the water dispersibility tends to decrease. On the other hand, the upper limit of the acid value is 70 mgKOH / g, preferably 50 mgKOH / g. When it is more than 70 mgKOH / g, the flexibility of the resulting film tends to be insufficient.

  Next, the said (A) component is manufactured by mixing the said chain aliphatic polyvalent isocyanate compound and a diol component, and making it urethane-react.

  The mixing ratio of the chain aliphatic polyvalent isocyanate and the diol component is an equivalent ratio, and the chain aliphatic polyvalent isocyanate compound / diol component is preferably 1.2 / 1.0 or more. /1.0 or more is preferable. When the ratio is smaller than 1.2 / 1.0, the viscosity of the urethane prepolymer is increased, and the dispersibility in water is reduced to cause aggregation and coarse particles may be generated. On the other hand, the upper limit of the mixing ratio is preferably 2.0 / 1.0, and preferably 1.9 / 1.0. If the ratio is larger than 2.0 / 1.0, the unreacted polyvalent isocyanate becomes excessive, and the dispersion state may deteriorate due to aggregation during foaming or foaming.

  The reaction temperature and reaction time of the urethane reaction can be selected from the same production conditions as those for ordinary urethane prepolymers. Specifically, the reaction temperature is preferably 50 to 120 ° C, and preferably 70 to 100 ° C. The reaction time is preferably 0.5 to 15 hours, and preferably 3 to 5 hours.

  The obtained component (A) may contain a carboxyl group. In this case, when at least a part is neutralized with a basic compound, the resulting aqueous dispersion is further stabilized, and when dispersed in a hydrophilic medium, as described later, without using a dispersant, It is also preferable because it can be dispersed. The basic compound is not particularly limited as long as it can neutralize the carboxyl group, and examples thereof include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, trialkylamines such as trimethylamine and triethylamine, and the like. It is done.

  Among the above basic compounds, trialkylamine is preferably used for at least part of the basic compound to be used from the viewpoint of water resistance.

  The obtained component (A) can be dispersed in water or a hydrophilic medium that is a mixture of water and a hydrophilic organic solvent (such as methanol or ethanol) to obtain an aqueous dispersion. When the obtained component (A) contains a carboxyl group that is at least partially neutralized, the component (A) itself can serve as a dispersant. It becomes possible to disperse in the hydrophilic medium without using it. In addition, when the obtained component (A) does not contain a carboxyl group, it can be dispersed in the hydrophilic medium by using a commonly used dispersant.

[Polymer of component (B)]
The polymerizable monomer as the component (B) refers to a monomer having radical polymerizability, and examples thereof include ester group-containing vinyl monomers, styrene and derivatives thereof, and other vinyl monomers.

  Examples of the ester group-containing vinyl monomer include (meth) acrylic acid ester compounds such as (meth) acrylic acid alkyl esters and (meth) acrylic acid alkoxyalkyl esters. In this specification, “(meth) acryl” means “acryl or methacryl”.

  Examples of the styrene and derivatives thereof include styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, and p-methylstyrene.

  Examples of the other vinyl monomers include vinyl group-containing monomers such as (meth) acrylic monomers other than the (meth) acrylic acid ester compounds, vinyl halide compounds, and polyfunctional unsaturated monomers. Such as body.

  Specific examples of the (meth) acrylic acid alkyl ester include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. Cyclohexyl (meth) acrylate, benzyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, isobornyl (meth) acrylate, and the like.

  Specific examples of the (meth) acrylic acid alkoxyalkyl ester include 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, 2-butoxyethyl (meth) acrylate, and the like.

  Specific examples other than the (meth) acrylic monomer other than the (meth) acrylic acid ester compound include (meth) acrylic acid, (meth) acrylonitrile, (meth) acrylamide and the like.

  Examples of the vinyl halide compound include vinyl chloride, vinylidene chloride, vinyl bromide, and vinyl fluoride.

Examples of the polyfunctional unsaturated monomer include aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene and derivatives thereof, N, N-divinylaniline, divinyl ether, divinyl sulfide, divinyl sulfone, and three or more. And compounds having a vinyl group.
In addition, each said polymerizable monomer may be used independently, and 2 or more types may be mixed and used for it.

  The component (B) can be emulsified and dispersed by mixing with the component (A) to form an aqueous dispersion, and a radical polymerization reaction can be performed to obtain a polymer of the component (B). As a mixing method of the component (B) to the component (A), a method of mixing before the formation reaction of the urethane prepolymer as the component (A), a formation reaction of the urethane prepolymer as the component (A) And a method of mixing before dispersion in the aqueous medium, a method of mixing after the formation reaction of the urethane prepolymer as the component (A) and after dispersion in the aqueous medium, and the like. Among these methods, when the method of mixing before the urethane polymerization of the component (A) is employed, the urethane resin and the polymer of the component (B) can be more closely combined in the obtained aqueous pressure-sensitive adhesive composition. Therefore, it is preferable.

  When the aqueous dispersion is prepared using any of the mixing methods described above, the mixing ratio of the component (A) and the component (B) in the aqueous dispersion is a solid content weight ratio, (A) / (B) = 20/80 or more is preferable, and 40/60 or more is more preferable. If it is smaller than 20/80, the dispersibility in water tends to be insufficient. On the other hand, the upper limit of the mixing ratio is preferably 90/10, and more preferably 80/20. If it is larger than 90/10, the initial tackiness may be lowered.

  Next, the radical polymerization is performed using a radical polymerization initiator using the aqueous dispersion containing the component (B). The polymerization temperature for this radical polymerization reaction is preferably about 50 to 100 ° C., and the reaction time is usually preferably about 2 to 16 hours.

  As the polymerization initiator, a polymerization initiator used in ordinary radical polymerization can be used. Examples of this radical polymerization initiator include persulfates such as ammonium persulfate, potassium persulfate, and sodium persulfate, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethyl). Radical polymerization initiators such as azo compounds such as valeronitrile), hydroperoxides such as hydrogen peroxide and t-butyl hydroperoxide, peroxides such as benzoyl peroxide and lauroyl peroxide, and the like. Or a mixture of two or more. These radical polymerization initiators can be used as a redox polymerization initiator in combination with a reducing agent such as sodium sulfite, sodium hydrogen sulfite, sodium thiosulfate, tartaric acid, L-ascorbic acid.

  After completion of the radical polymerization reaction, the remaining components of the polymerizable monomer may be polymerized by heating and aging at 50 to 80 ° C. for about 1 to 5 hours.

  The glass transition temperature of the polymer containing the component (B) in the aqueous pressure-sensitive adhesive composition thus obtained is required to be −10 ° C. or lower, and preferably −20 ° C. or lower. When it is higher than −10 ° C., the initial tackiness may be lowered. On the other hand, the lower limit of the glass transition temperature is not particularly limited, but a glass transition temperature lower than −80 ° C. is difficult to obtain, and this temperature may be the lower limit.

  Since the radical polymerization reaction and the heating / ripening reaction are aqueous reactions, a chain extension reaction of the component (A) may occur in this reaction. When this chain extension reaction occurs, the urethane prepolymer as the component (A) has an increased degree of polymerization and becomes polyurethane. In addition, after the heating / ripening reaction, for example, a compound having two or more active hydrogens capable of reacting with an isocyanate group such as ethylenediamine, hexamethylenediamine, isophoronediamine, and amino-modified silicone oil is actively used (A ) The component may be subjected to chain elongation reaction to obtain polyurethane.

  By these, the water-based adhesive composition containing the composite polymer mixture which consists of a urethane prepolymer (component (A) component) or a polyurethane, and the polymer which has a polymerizable monomer (B) as a structural component can be obtained. .

  EXAMPLES Hereinafter, although this invention is demonstrated in detail using an Example, this invention is not limited by a following example, unless the summary is exceeded. First, the evaluation method and the raw materials used will be described.

(Evaluation method)
[Glass-transition temperature]
The constituent weight fraction of each constituent monomer (polymerizable monomer) a, b,... In the vinyl polymer is Wa, Wb,..., And the glass transition of the homopolymer of each constituent unit a, b,. When the temperatures were Tga, Tgb,..., The Tg value of the vinyl polymer that was copolymerized was determined by the FOX formula shown below.
1 / Tg = Wa / Tga + Wb / Tgb +

[Initial adhesive strength]
Under normal temperature (23 ° C.), the adherend is a stainless steel (SUS) plate (manufactured by Nippon Test Panel Co., Ltd .: SUS304-BA) or a glass plate (commercial product), and peeled off 180 ° according to JIS Z 0237. The adhesion force was measured.
Moreover, the presence or absence of adhesive residue was determined visually according to the following criteria.
○… No glue residue.
×… There is glue residue.

[Adhesive strength with time]
The adherend is the above-mentioned SUS plate or glass plate, left for 24 hours at 60 ° C. and 90% Rh, and after 20 minutes at 20 ° C. and 50% Rh, conditions are adjusted, and 180 ° is drawn according to JIS Z 0237. The peel adhesion was measured.
Moreover, the presence or absence of adhesive residue was determined visually according to the following criteria.
○… No glue residue.
×… There is glue residue.

[Water resistance test]
The adherend was an SUS plate, immersed in tap water at normal temperature (23 ° C.) and 40 ° C., and the adhesive state after 24 hours was judged visually according to the following criteria.
○… No peeling.
×… There is peeling.
Moreover, the presence or absence of adhesive residue was determined visually according to the following criteria. In addition, when the adhesion state was “x”, it was not judged.
○… No glue residue.
×… There is glue residue.
−… Not judged because the adhesive state was “x”.

[Ball tack]
As described in JIS Z0237. Ball tack at an inclination angle of 30 degrees and a measurement temperature of 23 ° C. was measured by the DOW method. The number represents the ball number.

(raw materials)
[Polyisocyanate]
Trimethylhexamethylene diisocyanate: manufactured by Degussa-Huls: VESTANAT TMDI (trade name), hereinafter abbreviated as “TMDI”.
Hexamethylene diisocyanate: manufactured by Asahi Kasei Chemicals Corporation: Duranate 50M (trade name), hereinafter abbreviated as “HDI”.
Isophorone diisocyanate: manufactured by Degussa-Huls: VESTANAT IPDI (trade name), hereinafter abbreviated as “IPDI”.

[Polyol] (Hereinafter, “OHV” means a hydroxyl value (unit: mgKOH / g).)
Polytetramethylene ether glycol: Mitsubishi Chemical Corporation: PTMG1000, OHV: 109.8 mg KOH / g, number average molecular weight: 1022, hereinafter abbreviated as “PTMG”.
1, 4-butanediol: manufactured by Mitsubishi Chemical Corporation, hereinafter abbreviated as “14BD”.
Polypropylene glycol: manufactured by Daiichi Kogyo Seiyaku Co., Ltd .: Hiflex D2000 (trade name), OHV: 56.3 mg KOH / g, number average molecular weight: 1993, hereinafter abbreviated as “PPG”.

[Carboxyl group-containing polyol]
Dimethylolpropionic acid: Mallinckrodt Chemical Inc. “DMPA” manufactured by the company.

[Neutralizer]
Triethylamine: Wako Pure Chemical Industries, Ltd .: Reagent, hereinafter referred to as “TEA”.
Triethanolamine: Wako Pure Chemical Industries, Ltd .: Reagent, hereinafter referred to as “TEOA”.
Triisopropanolamine: manufactured by Wako Pure Chemical Industries, Ltd .: Reagent, hereinafter referred to as “TIPOA”.

[Polymerizable monomer]
・ Methyl methacrylate: manufactured by Mitsubishi Chemical Corporation, hereinafter referred to as “MMA”.
・ Butyl acrylate: manufactured by Mitsubishi Chemical Corporation, hereinafter referred to as “BA”.
-Ethyl acrylate: manufactured by Mitsubishi Chemical Corporation, hereinafter referred to as "EA".
-2-methoxyethyl acrylate: Mitsubishi Chemical Corporation: ethyl acrylate DC-1, hereinafter referred to as "2MEA".

[Polymerization initiator]
T-Butyl hydroperoxide: Wako Pure Chemical Industries, Ltd .: Reagent, hereinafter referred to as “PO”.
Ascorbic acid: Takeda Pharmaceutical Co., Ltd., hereinafter abbreviated as “AsA”.

(Example 1-7, Comparative Example 1-8)
To a four-necked flask equipped with a thermometer, a stirrer, and a reflux condenser, each component of the polyol and carboxyl group-containing polyol shown in Table 1 and each component of the polymerizable monomer are added in the amounts shown in Table 1, The internal temperature was set to 50 ° C., the amount of polyvalent isocyanate described in Table 1 was added, and the mixture was heated to 90 ° C. and reacted at this temperature for 5 hours to obtain a urethane prepolymer solution.
The obtained urethane prepolymer solution was cooled to 50 ° C., and the neutralizing agent in the amount shown in Table 1 was added to neutralize the carboxyl groups in the urethane prepolymer solution.
Next, ion-exchanged water (phase-inverted water) in the amount shown in Table 1 was dropped into this urethane prepolymer solution over 10 minutes to obtain a milky white aqueous dispersion.
Thereafter, this aqueous dispersion was kept at 50 ° C., a solution obtained by diluting PO in the amount shown in Table 1 with ion-exchanged water was added, and then a solution obtained by dissolving AsA with ion-exchanged water was added. Polymerization (radical polymerization reaction) was started. After completion of heat generation, the temperature was further raised to 70 ° C. and maintained for 3 hours to obtain an aqueous dispersion composite of polyurethane and vinyl polymer.
With respect to the obtained aqueous dispersion composite, the initial adhesive strength, the temporal adhesive strength, and the ball tack were measured according to the methods described above. The results are shown in Table 1.
In addition, the slight adhesiveness in this specification can be judged from a ball tack test. Further, the cohesiveness can be judged from the adhesive strength and the adhesive residue.

Claims (8)

(B) in an aqueous dispersion containing a urethane prepolymer (A) obtained by reacting a chain aliphatic polyvalent isocyanate compound and a diol component, and a polymerizable monomer (B). A composition obtained by polymerizing the components,
The acid value of the component (A) is 25 to 39 mgKOH / g,
(B) the glass transition temperature of the polymer obtained by polymerizing a component -80 ° C. or higher state, and are -32 ° C. or less,
An aqueous pressure-sensitive adhesive composition in which at least a part of the acid component in the component (A) is neutralized with a trialkylamine . The aqueous pressure-sensitive adhesive composition according to claim 1, wherein the diol component includes a polyether polyol and a carboxyl group-containing diol as essential components.   The aqueous pressure-sensitive adhesive composition according to claim 2, wherein the polyether polyol has a number average molecular weight of 300 to 2500.   The mixing ratio of the chain aliphatic polyvalent isocyanate compound and the diol component is an equivalent ratio, where the chain aliphatic polyvalent isocyanate compound / diol component is 1.2 to 2.0 / 1.0. Item 4. The aqueous pressure-sensitive adhesive composition according to any one of Items 1 to 3. The aqueous pressure-sensitive adhesive composition according to any one of claims 1 to 4 , wherein the trialkylamine is triethylamine. The aqueous pressure-sensitive adhesive composition according to any one of claims 1 to 5 , wherein the component (B) contains at least one selected from an ester group-containing vinyl monomer and styrene and derivatives thereof. The mixing ratio of the (A) component and the (B) component of the aqueous dispersion, in solid weight ratio, (A) / (B) = claims 1-6 which is a 20 / 80-90 / 10 The aqueous pressure-sensitive adhesive composition according to any one of the above. After the (B) component in the aqueous dispersion containing the urethane prepolymer (A) and the polymerizable monomer (B) is polymerized and the heat generation is completed, the component (A) The aqueous pressure-sensitive adhesive composition according to any one of claims 1 to 7 , which performs a chain extension reaction.