JPH0575769B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to an aqueous dispersion composition. More specifically, the present invention relates to an aqueous dispersion composition that can be particularly advantageously used as a heat sealant, such as adhesives, coating agents, surface treatment agents, and heat sealants for paper, metals, plastics, etc. [Prior art] Ethylene, α, β-unsaturated carboxylic acid and α,
A β-unsaturated carboxylate copolymer, one or more monomers selected from group (a) that have a glass transition temperature of 70°C or higher when made into a single polymer, and A copolymer obtained by copolymerizing one or more monomers selected from group (D) of other monomers that can be copolymerized and have a glass transition temperature of 50°C or less when made into a single polymer. An aqueous dispersion consisting of a polymer composition has been proposed in JP-A-57-137339. In this proposal, styrenic hydrocarbons are used as the monomer group (a).
It has been shown that (d) and α,β-unsaturated carboxylic acid ester (e) can be selected as the monomer group (D), respectively, but it is preferable that the grafting ratio is 10% by weight or more. However, there has been little investigation, and the graft rate is only 41% in Example 1.
Only examples are shown. However, according to the studies of the present inventors, styrenic hydrocarbons (d)
In the copolymerization of α,β-unsaturated carboxylic acid ester (e), when an aqueous dispersion of the copolymer as specifically disclosed in the publication is used as a heat sealant for plastic film or paper. , although the low-temperature heat-sealing properties were somewhat excellent, the hot-tack properties were still not sufficient. [Problems to be Solved by the Invention] The object of the present invention is to provide an aqueous dispersion composition that provides excellent hot-tack properties without reducing heat-sealing strength, especially when used as a heat-sealing agent for plastic films and the like. be. [Summary of the Invention] The present invention consists of ethylene (a), an α,β-unsaturated carboxylic acid (b), and an α,β-unsaturated carboxylic acid metal salt (c), and (b) and (c) The total content of (c) to (b) is in the range of 4.5 to 5.5 mol%, and the molar ratio of (c) to (b) is
Styrenic hydrocarbon (d) and α, β-unsaturated carboxylic acid ester (e) to 100 parts by weight of copolymer (A) in the range of 1.1 to 1.5, the sum of (d) and (e) The amount
Kraft polymerization is carried out in an amount of 25 to 60 parts by weight and a weight ratio of (e) to (d) in a range of 1 to 1.7,
The gist of this invention is an aqueous dispersion composition comprising a copolymer composition in which the total kraft ratio of (d) and (e) to (A) is 75% by weight or more. [Ionomer (A)] The ionomer (A) used in the present invention has a specific component content. That is, ethylene
(a), α, β-unsaturated carboxylic acid (b) and α, β-unsaturated carboxylic acid metal salt (c), and the total content of (b) and (c) is 4.5 to 5.5 mol%. within the range and (c)
The molar ratio of the content to (d) is in the range of 1.1 to 1.5. If the total content of (b) and (c) is outside the above essential range, if it is less than 4.5 mol%, it will be difficult to obtain a stable aqueous dispersion, and if it exceeds 5.5 mol%, the cohesive force of the resin will decrease, resulting in adhesion. If the molar ratio of (c) to (b) deviates from the above-mentioned essential range due to insufficient strength, it will still be difficult to obtain a stable aqueous dispersion. Examples of the α,β-unsaturated carboxylic acid (b) which is a component of the ionomer (A) include acrylic acid, methacrylic acid, fumaric acid, itaconic acid, maleic acid, etc. As acid metal salts (c), sodium, potassium,
An example is lithium salt. A particularly preferred component (b) is methacrylic acid, and a particularly preferred component (c) is methacrylic acid sodium salt.
In addition to the above components (a), (b) and (c), the ionomer (A) may also contain esters of the above α,β-unsaturated carboxylic acids, such as linear or branched lower chains of acrylic acid and methacrylic acid. Alkyl esters, ammonium salts of the α,β-unsaturated carboxylic acids, vinyl esters such as vinyl acetate, vinyl alcohols, etc. may be included, but these may be used as the metal salts of the α,β-unsaturated carboxylic acids (c). Usually less than half the molar content is necessary to obtain a stable aqueous dispersion. Note that other components are not included in the calculation of the above-mentioned essential ranges of components (a), (b), and (c). [Styrenic hydrocarbon (d)] Examples of the styrenic hydrocarbon (d) used in the production of the composition of the present invention include styrene, α-methylstyrene, vinyltoluene, etc. Among them, styrene is preferable. [α,β-unsaturated carboxylic acid ester (e)] Examples of the α,β-unsaturated carboxylic acid ester (e) used in the production of the composition of the present invention include methyl (meth)acrylate, (meth) (Meth) such as ethyl acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, sec-butyl (meth)acrylate, iso-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, etc. ) acrylic acid alkyl esters, among which n-butyl acrylate (n-butyl acrylate) is preferred. [Manufacturing method] The aqueous dispersion composition of the present invention comprises an ionomer (A)
It can be obtained by emulsion graft polymerization of a styrenic hydrocarbon (d) and an α,β-unsaturated carboxylic acid ester (e) as monomers in an aqueous dispersion state. The aqueous dispersion of ionomer (A) can be obtained, for example, by the method disclosed in JP-A-51-62890. Furthermore, when grafting, a persulfate or an organic peroxide is usually used as a polymerization initiator.
These initiators include ammonium persulfate,
Examples include benzoyl peroxide-dimethylaniline. Further, during emulsion graft modification polymerization, it is not necessary to use a surfactant, but it is preferable to use it to stabilize the reaction system. Preferred surfactants include, for example, sodium lauryl sulfate, sodium dodecylbenzenesulfonate, and sodium oleate. The amount of the monomers styrenic hydrocarbon (d) and α,β-unsaturated carboxylic acid ester (e) used in producing the composition of the present invention is based on 100 parts by weight of the ionomer (A). ) and (e) in a total amount of 25 to 60 parts by weight, and the weight ratio of (e) to (c) is in a range of 1 to 1.7. Also, the grafting rate to iomer (A) relative to the total usage of monomers (d) and (e) (total grafting rate)
is 75% by weight or more. If the total amount of monomers (d) and (e), the weight ratio of monomer (e) to (d), and the total grafting rate are outside the above ranges, the resulting heat sealing agent will lack adhesiveness, and Hot-tack properties (hot-sealing properties: adhesive strength during hot conditions immediately after heat-sealing) become lacking. Furthermore, if the weight ratio of monomer (e) to monomer (d) exceeds 1.7, the coated film will become sticky in addition to the above. When producing the composition of the present invention, in addition to the above monomers (d) and (e), (meth)acrylic acid, acrylonitrile, acrylamide, etc. may be used simultaneously within a range that does not impair the effects of the present invention. . [Aqueous dispersion composition] The aqueous dispersion composition of the present invention contains an ionomer (A).
In addition to the grafted product in which monomers (d) and (e) are grafted, the monomer (co)polymer of monomers (d) and (e) is included, but it is usually not necessary to remove this. The total concentration (solid content concentration) of the graft material and the homo (co)polymer in the composition of the present invention is usually 10
from 20 to 60% by weight, preferably from 20 to 50% by weight. In addition to the above-mentioned components, the composition of the present invention may include various emulsifiers, thickeners, face weights, PH adjusters, binders, dispersion aids, film-forming agents, etc., depending on the purpose and within the range that does not impair the effects of the present invention. Auxiliary agents, lubricants, antiblocking agents, coloring agents, etc. may be included. [Applications/Effects] The aqueous dispersion composition of the present invention is disclosed in, for example, JP-A-57
It can be used for applications such as those described in JP-A-137339. That is, it can be applied directly to paper, metals, and plastics to provide a thermal adhesive with excellent adhesive strength. It is also possible to thermally bond the coating films formed by this coating or the coating film and other paper, metal, or plastic by heat sealing. Still another method is to coat a biaxially oriented polypropylene film, polyester film, nylon film, etc. with a vinylidene chloride resin layer in order to impart gas barrier properties.
Alternatively, an anchor coating agent may be used for the purpose of further improving the adhesion between these films and the coating film made of the composition of the present invention. In the latter,
It is also possible to previously apply an anchor coat to the aforementioned film and then apply the composition of the present invention thereon to form a heat-sealable coating. As the anchor coating agent in this case, polyethyleneimine-based, polyester-based, polyurethane-based, polyether-based, organic titanium-based, polybutadiene-based, etc. can be used, although it varies depending on the type of film to be coated. The substrates used for coating the composition of the present invention generally include papers such as kraft paper, high-quality paper, coated paper, metal foils such as aluminum and iron, plates, sheets, etc.
In addition, examples of plastics include polyethylene and ethylene-vinyl acetate copolymer. , ethylene resins such as ethylene ionomers, polystyrene, AS resins,
Examples include polyvinyl chloride, polyvinylidene chloride, polymethyl methacrylate, polyester, and nylon, and it goes without saying that these materials can be applied to sheets, films, molded products, foams, and other shapes of all kinds. Naturally, copolymers such as vinyl chloride-vinyl acetate copolymer, styrene-butadiene copolymer, and mixtures thereof are also included. The composition of the present invention can be used as a coating agent and a surface treatment agent for various substrates in addition to the above-mentioned thermal adhesive. The coating film formed from the composition of the present invention has high tensile strength, is flexible, transparent, has excellent thermal adhesion and heat sealing properties, is resistant to blocking, and has excellent adhesive strength and hot-tack properties. Much better than the traditional one. Therefore, the heat-sealed portion does not peel off even when the contents are filled not only after cooling, but also during the hot period immediately after heat-sealing, and an excellent heat-sealing agent can be obtained. Hereinafter, the present invention will be specifically explained with reference to Examples. [Example] Example 1 A copolymer consisting of ethylene, methacrylic acid, and its Na salt, in which the total amount of methacrylic acid and its Na salt is 5.4 mol%, and the content of the Na salt is 5.4 mol%.
A small amount of surfactant (sodium laurate) and polymerization initiator (potassium persulfate) were added to 100 polymerized parts of an aqueous dispersion of 3.2 mol% ionomer resin with a solid content concentration of 30%, and the mixture was heated to 80°C. ,
4.5 parts of styrene and 7.5 parts of n-butyl acrylate
When emulsion polymerization was carried out by dripping over a period of time,
A milky white homogeneous aqueous dispersion with a solids concentration of 35% by weight was obtained. The polymer obtained by drying this aqueous dispersion is
The grafting rate of styrene and n-butyl acrylate was calculated to be 93% from the weight of the polymer after heating at 75° C. for 2 hours in MEK to remove non-grafted polymer. This aqueous dispersion was applied to an OPP film coated with a urethane-based anchor coating agent, dried with hot air to form a coating film with a thickness of 5μ, and the coated surfaces were bonded to JISZ1707.
1Kg/cm ² for 1 second at 120℃ using a method based on
After thermally adhering with the pressure of
g/15mm. Further, when the hot tack property was measured by the method described below, the peeling distance was 2 cm.

[Table] Method for evaluating hot tack properties Heat sealing is performed in the same manner as in the evaluation of adhesive strength above, but at the same time as the heat sealing is completed, that is, the seal bar of the heat sealing machine is separated from the test piece film. At the same time, the combed film was peeled off in a T-shape under a load of 90 g, and the peeling distance of the film at this time was expressed as a value in cm. The shorter the peeling distance, the
Excellent hot tack properties. Examples 2 to 5, Comparative Examples 1 to 5 Table 1 shows the degree of adhesion and hot-tack properties (peel distance) when aqueous dispersions with different compositions were used in heat sealing materials. The aqueous dispersion was produced in the same manner as in Example 1, but in Comparative Example 5, the monomer dropwise addition time was 30 minutes.

Claims (1)

[Claims] 1 Consisting of ethylene (a), α, β-unsaturated carboxylic acid (b) and α, β-unsaturated carboxylic acid metal salt (c), the total content of (b) and (c) is 4.5 to 5.5 mol %, and the content molar ratio of (c) to (b) is in the range of 1.1 to 1.5 per 100 parts by weight of copolymer (A),
Styrenic hydrocarbon (d) and α, β-unsaturated carboxylic acid ester (e), the total amount of (d) and (e) is 25 or
60 parts by weight, and the weight ratio of (e) to (d) is in the range of 1 to 1.7, and is obtained by kraft polymerization to (A).
An aqueous dispersion composition comprising a copolymer composition in which the total grafting ratio of (d) and (e) is 75% by weight or more.