JP5006535B2 - Adhesive composition - Google Patents

Description

  The present invention relates to an aqueous adhesive composition having excellent low-temperature film-forming properties, adhesive strength, and coating workability.

Conventionally, vinyl acetate resin emulsions that are excellent in adhesion performance, coating workability, and the like have been widely used as adhesives that are water-based and easy to use.
However, since the vinyl acetate resin emulsion does not have a low-temperature film-forming property and cannot be used as it is at around 0 ° C., it is indispensable to use it as a form containing a plasticizer.
In recent years, however, plasticizers are suspected of being an environmental hormone, so that an adhesive that does not contain them has been demanded.

As a method of avoiding the blending of the plasticizer, a method of preparing vinyl acetate by emulsion polymerization in the presence of an ethylene / vinyl acetate copolymer resin emulsion or an acrylic resin emulsion has been proposed.
However, the former has problems in heat resistance, coating workability, etc., while the latter has excellent low-temperature film-forming properties and initial adhesion performance, but has poor coating properties at low temperatures and slows the polymerization rate of vinyl acetate. There was a problem that the production efficiency was lowered, and there was room for improvement.

JP 2003-213235 A JP 2001-294833 A

  The present invention has the above-mentioned problems, that is, it does not contain a plasticizer, does not lengthen the production time, and has many performances such as low-temperature film-forming properties, low-temperature adhesion properties, initial adhesion performance and application workability. It is intended to provide an adhesive composition.

As a result of intensive studies, the inventors have found that, in terms of solid content, 100 parts by weight of vinyl acetate resin emulsion (hereinafter PVAc), 0.1 to 100 parts by weight of ethylene / vinyl acetate resin emulsion (hereinafter EVA), acrylic As described above, the adhesive composition prepared by blending 0.1 to 20 parts by weight of a resin emulsion (hereinafter referred to as AE) and 0.1 to 5 parts by weight of a polyvinyl alcohol solution (hereinafter referred to as PVA liquid) solves the problem as described above. I was able to.

Since the adhesive composition according to the present invention has many performances such as low film-forming property, low-temperature adhesiveness, initial adhesive performance and coating workability, the production time does not become long. Regardless of the season, it can be used safely for various purposes.
In addition, since it does not contain a plasticizer suspected of being an environmental hormone, it can be used without fear of environmental pollution.

The PVAc according to the present invention is prepared, for example, by emulsion polymerization of vinyl acetate or a comonomer copolymerizable with vinyl acetate with a polymerization initiator in an aqueous system containing polyvinyl alcohol (hereinafter, blended PVA) as a protective colloid.
When the blended PVA is blended, it acts as an emulsifier during emulsion polymerization, and adjustment to an appropriate viscosity as an adhesive, application workability, and initial adhesive force are improved.
For blended PVA, the average degree of polymerization is 300 to 4000, and any of partially saponified products, intermediate saponified products, and completely saponified products can be used. However, partially saponified PVA may be used for woodworking applications. From the viewpoint of improving coating properties. About the compounding quantity, 2-40 weight part is mix | blended with respect to 100 weight part of resin solid content of PVAc, and 2 or more types from which polymerization degree, saponification degree, etc. differ depending on the case can also be used together.
Further, in some cases, modified PVA such as acetoacetylated PVA, carboxyl group-modified PVA, and the like may be employed.

  Various comonomers that can be copolymerized with vinyl acetate include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, lauryl (meth) acrylate, and 2-ethylhexyl (meth) acrylate ( Hydroxyl group-containing acrylic monomers such as (meth) acrylic acid ester, vinyl propionate, vinyl versatate, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, (meth) acrylonitrile, (N-methylol) Examples include acrylamide, (meth) acrylic acid, itaconic acid, maleic acid, and fumaric acid.

  Examples of emulsifiers include nonionic surfactants such as polyoxyethylene alkylphenol ether and polyoxyethylene stearic acid ester, potassium oleate, sodium lauryl sulfate, sodium dodecylbenzenesulfonate, polyoxyethylene alkylphenol ether sulfate or sulfonate, alkylbenzene sulfate. Anionic surfactants such as phonates, cationic surfactants such as stearylamine hydrochloride and lauryltrimethylammonium chloride, amphoteric surfactants such as laurylbetaine and lauryldimethylamine oxide may be used, or combined with PVA Good.

Examples of the polymerization initiator include organic peroxides such as aqueous hydrogen peroxide and benzoyl peroxide, as well as ammonium persulfate, potassium persulfate, sodium persulfate, azobisisobutylnitrile, and the like.
It can also be used as a redox system in combination with a reducing agent such as tartaric acid and ascorbic acid.
0.05-2 weight part is employ | adopted for the usage-amount of a polymerization initiator with respect to 100 weight part of vinyl acetate.

  As PVAc to be prepared, those having a resin solid content of 30 to 60% by weight and a viscosity at 20 ° C. of 0.1 to 300 Pa · s are suitable for preparing an adhesive composition.

AE is obtained by emulsion polymerization of an acrylic monomer or a comonomer copolymerizable therewith in the presence of an emulsifier, a polymerization initiator, a polymerization regulator, and the like. ) Methyl acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, lauryl (meth) acrylate, 2-ethylhexyl (meth) acrylate, etc. (meth) acrylate, 2-hydroxyethyl (meth) acrylate And hydroxyl group-containing acrylic monomers such as 3-hydroxypropyl (meth) acrylate, (meth) acrylonitrile, (N-methylol) acrylamide and the like.
Examples of the comonomer used in combination with these acrylic monomers include styrene, vinyl acetate, (meth) acrylic acid, itaconic acid, maleic acid, and fumaric acid.
AE preferably has a Tg of 0 ° C. or lower, preferably 0 to −60 ° C., because of the low-temperature film-forming property and low-temperature adhesiveness of the prepared adhesive composition. It is necessary to select such acrylic monomers and comonomers.
When Tg exceeds 0 ° C., there is a concern that the film forming temperature of the prepared resin emulsion is not sufficiently lowered, which is not preferable. Moreover, if it is less than -60 degreeC, since the prepared adhesive composition becomes too soft, cohesion force becomes low and adhesive performance is reduced, it is not suitable.

  Emulsion polymerization of AE can be performed by a known method. For example, in a heatable reaction vessel in which a reflux condenser, a monomer dropping port and a stirrer are laid, the polymerization as described above is carried out in an aqueous solution containing an emulsifier. After adding the initiator, the acrylic monomer is added dropwise at a temperature of 50 to 90 ° C. with stirring until the conversion of the acrylic monomer is 90% or more, preferably 95% or more.

  For AE, those obtained as described above, or commercially available acrylic resin emulsions, etc. are used, but those having a Tg of 0 ° C. or lower as described above lower the PVAc film forming temperature. Suitable for use from the viewpoint.

EVA having a Tg of 0 ° C. or lower is suitable for use.
When Tg exceeds 0 ° C., EVA itself tends to lack flexibility, the flexibility of the prepared adhesive composition is impaired, and there is a concern that low-temperature adhesiveness and initial adhesive force may be reduced, which is not preferable.

  As the polyvinyl alcohol used in the PVA liquid, any of partially saponified products, intermediate saponified products, and completely saponified products having an average degree of polymerization of 300 to 4000 can be used. Although there is no restriction | limiting in particular regarding the density | concentration of a PVA liquid, 10 to 30 weight% is preferable. If it is less than 10% by weight, the non-volatile content is greatly reduced at the time of blending, which may not be preferable. If it exceeds 30% by weight, the viscosity of the PVA liquid becomes high and it may be difficult to handle. Two or more types having different degrees of polymerization and saponification may be used in combination. Further, in some cases, modified PVA, for example, acetoacetylated modified polyvinyl alcohol, carboxyl group modified polyvinyl alcohol or the like may be used or used in combination.

The adhesive composition according to the present invention is prepared by blending PVAc, EVA, AE and PVA liquid, and the blending procedure is not particularly limited, but other blending materials are added to PVAc as the main raw material from the manufacturing process. The operation procedure of adding and mixing is convenient from the viewpoint of the manufacturing process.
A preferable blending ratio of the adhesive composition is 0.1 to 100 parts by weight of EVA, 0.1 to 20 parts by weight of AE, and 0.1 to 5 parts by weight of PVA liquid with respect to 100 parts by weight of PVAc in terms of resin solids, Depending on the blending ratio outside these preferable blending ratios, the expected performance cannot be obtained.

  The adhesive composition according to the present invention has properties such as low-temperature film-forming properties and coating workability.

Hereinafter, the present invention will be described in detail with reference to examples and comparative examples. Note that parts by weight are simply indicated as parts, and% by weight is simply indicated as%.
Synthesis example of PVAc 558 parts of water was charged in a reaction vessel equipped with a stirrer, a temperature controller, a reflux condenser, and a thermometer, and 55 parts of polyvinyl alcohol (saponification degree 88 mol%, average polymerization degree 1700) was added, and 80 ° C. The solution was heated until dissolved, and while maintaining the temperature in the system at 80 ° C., a catalyst prepared by dissolving 1 part of ammonium persulfate in 20 parts of water and 330 parts of vinyl acetate were added dropwise over 3 hours to proceed the emulsion polymerization. The polymerization reaction rate was 99.3%. The property values of the obtained PVAc are shown in the table.

AE
Ultrazol C-70 (Tg-30 ° C., non-volatile content 55%) manufactured by Ganz Kasei Co., Ltd. was used. The property values are shown in Table 1.

EVA
Denka EVA tex # 59 (Tg-18 ° C., non-volatile content 56%) manufactured by Denki Kagaku Kogyo Co., Ltd. was used. The property values are shown in Table 1.

Preparation of PVA A 15% aqueous solution of Denkapoval B-17 (saponification degree 88 mol%, polymerization degree 1700) from Denki Kagaku Kogyo Co., Ltd. was prepared. The property values are shown in Table 1.

Preparation of adhesive composition In a container equipped with a stirrer, the above-prepared PVAc, EVA, AE and PVA liquid were blended as shown in Table 2 (the blending numerical values in Table 2 represent parts) of Examples and Comparative Examples. An adhesive composition was obtained. The characteristic values and performance of the prepared adhesive composition are shown in Table 2.

Test / Evaluation Method Viscosity Pa · s / 23 ° C. BH type viscometer Average value of 4 rpm and 10 rpm Normal-state adhesive strength Based on JISK6804 (2003 edition) 8.8, the block shear test was done using the cover plate of the edge.
◯: Adhesive strength 10 N / mm ² or more ×: Adhesive strength 10 N / mm ^{2 or} less Water-resistant adhesive strength Based on JISK6804 (2003 edition) 8.8, a test specimen was prepared using a scabbard scabbard, immersed in 30 ° C water for 3 hours, and then immersed in 23 ° C water for 10 minutes for testing. It was.
◯: Adhesive strength 3 N / mm ² or more ×: Adhesive strength 3 N / mm ^{2 or} less Low temperature film-forming property / Measured according to JISK6804 (2003 edition) 6.8.2 using a temperature gradient heat plate type minimum film-forming temperature measuring device.
5. Application workability / Adhesive composition adjusted to 5 ° C. on 30 cm square plywood was applied with 100 g / m ² with a rubber roller.
◯: Adhesive has good applicability and can be applied uniformly.
X: The applicability | paintability of an adhesive agent is bad and cannot apply | coat uniformly.

The adhesive composition according to the present invention is excellent in low-temperature film-forming properties, low-temperature adhesiveness, initial adhesive strength, and application workability, so that it can be used safely for all seasons, especially for woodworking, regardless of winter or summer. Available to:

Claims (1)

0.1 to 100 parts by weight of ethylene / vinyl acetate resin emulsion, 0.1 to 20 parts by weight of acrylic resin emulsion, and 0.1 to 5 parts by weight of polyvinyl alcohol aqueous solution with respect to 100 parts by weight of vinyl acetate resin emulsion in terms of solid content An adhesive composition, wherein parts are blended.