JPH0416507B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an adhesive composition, and more particularly to a paper adhesive composition containing a vinyl ester resin emulsion as a main component. Vinyl ester resin emulsion is for paper tubes,
It is widely used as a paper adhesive for making bags, pasting cardboard sheets, etc. However, in recent years, there has been a strong demand for increased lamination speed, and machine speeds have become significantly faster. For this reason, conventional adhesives have insufficient initial adhesion performance, and adhesives with excellent initial adhesion properties are strongly desired. One way to improve initial adhesion is to increase the resin concentration of the adhesive. However, from the viewpoint of fluidity and adhesive performance, most paper adhesives are mainly composed of vinyl ester resin emulsions using polyvinyl alcohol (hereinafter abbreviated as PVA) as a protective colloid, and in this case, the resin concentration is If the concentration is increased, the viscosity increases significantly, so it has been difficult to industrially produce emulsions with high concentrations. The present inventors proposed a method using the general formula R-S-() [where R is an alkyl group having 1 to 20 carbon atoms which may have a hydroxyl group or a carboxyl group] in place of the conventionally used PVA. and S represents a sulfur atom] at one end.
Emulsion polymerization of vinyl ester monomers with 20 to 300 PVA polymers as protective colloids yields emulsions with high solids content and relatively low viscosity, and this emulsion is also effective in initial adhesion during paper/paper lamination. The inventors have discovered that this material has excellent properties, and have arrived at the present invention. The average degree of polymerization of PVA used in the present invention is 20~
The degree of polymerization is determined by the Nakajima method [Akio Nakajima: Kobunshi 6 451 (1949)] by acetylating the PVA to make polyvinyl acetate (hereinafter abbreviated as PVAc) and then measuring the viscosity in acetone. It is to be determined. PVA with an average degree of polymerization of 20 to 300 having a group represented by the general formula () at one end
An emulsion obtained by emulsion polymerization mainly made of vinyl acetate with a protective colloid has a lower viscosity at the same solid concentration than an emulsion obtained in the same way using ordinary PVA. It is possible to further increase the value from around 40 to 50% (weight), and it is possible to increase it to 55% or more, especially 60% or more. PVA of the present invention
The average degree of polymerization of the system polymer is 20 to 300, preferably 50
~200, and the degree of saponification is preferably 70 to 99 mol%. If the average degree of polymerization is less than 20, the stability of the emulsion will be insufficient;
If it exceeds , the viscosity reduction effect will be reduced. Specific examples of the alkyl group having 1 to 20 carbon atoms which may have a hydroxyl group or carboxyl group for R in the general formula () include a methyl group,
Ethyl, n-propyl, n-butyl, t-butyl, n-hexyl, n-heptyl, 2-ethylhexyl, n-dodecyl, hydroxyethyl, 2,
3-dihydroxypropyl, carboxymethyl,
Examples include carboxyethyl, which has such a terminal group at one end of the molecule and has an average degree of polymerization.
For example, when PVA of 20 to 300 is used to polymerize vinyl esters, particularly vinyl acetate, in the presence of mercaptans represented by R-SH (R is the same as above), the method of adding the mercaptans to the polymerization system must be strictly controlled. It can be obtained by saponifying polyvinyl acetate obtained by controlling the polyvinyl acetate by a conventional method. Among these, R has 8 carbon atoms
PVA, which is an alkyl group of ˜20, has a particularly large stabilizing effect and is therefore preferable. The above into the emulsion used in the present invention
The amount of PVA blended is 1 to 1 to vinyl ester resin.
30% by weight, preferably 2 to 20% by weight, but in addition to the above-mentioned PVA, within a range that does not impair the effects of the present invention, ordinary PVA with a high degree of polymerization, modified PVA,
Protective colloids such as methyl cellulose and hydroxyethyl cellulose can be used, and conventionally known surfactants can also be used in combination within a range that does not impede adhesive performance. The vinyl ester resin emulsion which is the main component of the adhesive composition of the present invention is one obtained by emulsion polymerization of vinyl acetate alone using the above-mentioned PVA;
Alternatively, polymerizable unsaturated compounds copolymerizable with vinyl acetate, such as acrylic esters such as methyl acrylate, ethyl acrylate, and 2-ethylhexyl acrylate, and methacrylic acids such as methyl methacrylate, ethyl methacrylate, and butyl methacrylate. Esters, α-olefins such as ethylene and isobutylene, dibutyl maleate, dioctyl maleate, vinyl chloride, acrylic acid,
Unsaturated carboxylic acids such as methacrylic acid and maleic acid, N-methylol acrylamide, vinyl propionate, vinyl persatinate (Veova-10)
It is obtained by emulsion copolymerization of one or more monomers such as vinyl esters of carboxylic acids having 3 to 12 carbon atoms (trade name of Ciel Chemical Co., Ltd.). Among these, acrylic esters that effectively internally plasticize vinyl acetate resin, ethylene, and 3 carbon atoms.
A copolymerized emulsion with a vinyl ester of a carboxylic acid of -12 is preferably used. In particular, ethylene-vinyl acetate copolymer emulsion having an ethylene content of 10 to 40% by weight is preferably used because it exhibits good adhesion to water-repellent paper and plastic-laminated so-called hydrophobic paper. Furthermore, it is effective that the emulsion used in the present invention has a solid content concentration of 55% by weight or more, preferably 60% or more, and if it is less than 55%, the initial adhesiveness is low. There is no particular upper limit to the solid content concentration, but it is approximately 70% by weight. In the adhesive composition of the present invention, necessary additives such as a plasticizer, a fungicide, an antifoaming agent, and a thickener are added to the emulsion according to the individual purpose. The present invention will be described in more detail below with reference to Examples, but these Examples are not intended to limit the present invention in any way. In the examples, parts and percentages are based on weight unless otherwise specified. Example 1 A reactor equipped with a stirrer, a reflux condenser, and a nitrogen inlet tube was prepared with a hydroxyethylthiyl group at one end, an average degree of polymerization of 120, and a degree of saponification of 87.5 mol%.
After charging 2 parts of PVA and purging with nitrogen, 35 parts of ion-exchanged water was added and the mixture was heated and stirred at 80°C.
After PVA was completely dissolved, the mixture was cooled to room temperature under a nitrogen stream, 7.5 parts of vinyl acetate monomer was added, and the temperature was raised to 70°C while stirring. After the internal temperature reached 70°C, continuous addition of 3.5 parts of a 1% aqueous hydrogen peroxide solution and 2 parts of a 5% Rongalite aqueous solution was started to initiate polymerization. After initiation of polymerization, 92.5 parts of vinyl acetate monomer was uniformly added over 2 hours. The above during this time
A PVA aqueous solution (concentration: 30%) in which 6 parts of PVA was dissolved in 14 parts of ion-exchanged water substituted with nitrogen was continuously added. After the addition of the vinyl acetate monomer was completed, the temperature was raised to 80°C and maintained for 1 hour to complete the polymerization. The obtained polyvinyl acetate emulsion has a solid content concentration of
65.7%, and the viscosity was 6500 mPas·s (30°C B-type viscometer). 5 parts of dibutyl phthalate (DBP) was added to 100 parts of solid content of this emulsion,
Initial adhesion was evaluated using the Tappi method described below. The results are shown in Table 1, and as is clear from the comparative examples described later, it is recognized that the initial adhesion is considerably improved compared to the conventional emulsion using PVA with a high degree of polymerization. [Initial adhesion test] Tappi Monograph Series Vol. 26, p. 74 (1963)
This is the method described. Liner paper (basis weight
Apply adhesive to 200g/m ² ), laminate, and immediately
Peeling was performed at 180° and expressed as the time (seconds) for the paper tear rate to exceed 50%. Example 2 Using the same reactor as in Example 1, having HOOC- _CH2 - _CH2- S- at one end instead of PVA used in Example 1, average degree of polymerization 150, degree of saponification 89.0 mol% The same operation as in Example 1 was performed except that PVA was used. The obtained polyvinyl acetate emulsion had a solid content concentration of 64.8% and a viscosity of 5800 mPas-s (30
℃). Initial adhesion was evaluated by adding 5 parts of DBP to 100 parts of solid content of this emulsion. The results are shown in Table-1. Comparative Example 1 In place of PVA in Example 1, ordinary PVA with an average degree of polymerization of 500 and a degree of saponification of 88.0 mol% was used.
A similar polymerization was attempted. However, it is added sequentially during polymerization.
When the concentration of PVA aqueous solution is 30%, the viscosity is too high.
Since addition was no longer possible, a 20% aqueous PVA solution was used, and in order to obtain an emulsion with the same solid content concentration as in Example 1, the amount of ion-exchanged water at the initial stage of polymerization was reduced to 25 parts. After the polymerization started, addition of vinyl acetate monomer was started, but when 62.5 parts out of 92.5 parts were added, the viscosity increased significantly, resulting in poor stirring and a large number of aggregates were formed. Comparative Example 2 Using the same reactor as Example 1, the average degree of polymerization
1750, 8 parts of normal PVA with saponification degree of 87.5 mol%,
After adding 98 parts of ion-exchanged water and dissolving it by heating, 10 parts of vinyl acetate monomer was added. The temperature was then raised to 70°C, and polymerization was carried out with 3 parts of a 1% aqueous hydrogen peroxide solution and 2 parts of a 5% aqueous tartaric acid solution. After starting the polymerization, 90 parts of vinyl acetate monomer was added uniformly over 2 hours, and after the addition was completed, the mixture was maintained at 80°C for 1 hour. The obtained polyvinyl acetate emulsion had a solid content concentration of 50.4% and a viscosity of
It was 34500 mPas-s (30°C). 5 parts of DBP was added to 100 parts of the solid content of the emulsion, and the initial adhesion was evaluated. The results are shown in Table-1. Example 3 In a pressure-resistant autoclave equipped with a repellent stirrer, a nitrogen inlet tube, and various drug injection pumps, a molecule with an n-dodecylthiyl group at one end and an average polymerization degree of 110,
After heating and dissolving 4.5 parts of PVA with a saponification degree of 90.2 mol% in 60 parts of ion-exchanged water, 10 parts of vinyl acetate monomer was added.
After purging with nitrogen, the temperature was raised to 60°C, and ethylene was pressurized to 45 kg/cm ² . 1% peroxide aqueous solution and 5
Polymerization was carried out using a % Rongarit aqueous solution.
After initiation of polymerization, 90 parts of vinyl acetate monomer was continuously added over 3 hours. The obtained ethylene-vinyl acetate copolymer emulsion had a solid content concentration of 66.3% and a viscosity of 3800 mPas・s.
(30°C), and the ethylene content was 19.5%. Table 1 shows the results of initial adhesion using this emulsion. Comparative Example 3 Average degree of polymerization instead of PVA used in Example 3
Polymerization was carried out in the same manner as in Example 3, except that ordinary PVA with a saponification degree of 87.5 mol % was used, but when 70 parts of vinyl acetate monomer was added, stirring became impossible due to an increase in viscosity. Comparative Example 4 Polymerization was carried out in the same manner as in Comparative Example 3, except that the amount of ion-exchanged water in Comparative Example 3 was changed to 90 parts, and the solid content concentration was 56.0%.
Viscosity 3500mPas・s (30℃), ethylene content 18.0%
An ethylene-vinyl acetate copolymer emulsion was obtained. The results of the initial adhesion of this emulsion are shown in Table 1.

[Table] Comparative Example 5 In place of PVA used in Example 3, average degree of polymerization
Polymerization was carried out in the same manner as in Example 3 except that ordinary PVA with a saponification degree of 88 mol % was used, but when 80 parts of vinyl acetate monomer was added, the viscosity increased significantly and stirring became impossible. Comparative Example 6 Instead of PVA used in Example 3, average degree of polymerization
Polymerization was carried out in the same manner as in Example 3, except that ordinary PVA with a saponification degree of 87.5 mol% was used. When 80 parts of vinyl acetate monomer was added, stirring became impossible due to the increase in viscosity, and many aggregates were formed. did. Comparative Example 7 PVA2 charged before the start of polymerization in Example 1
1 part of polyoxyethylene nonyl phenyl ether (degree of polymerization of oxyethylene units: 20) was used instead of 1 part, and 3 parts of the above polyoxyethylene nonyl phenyl ether was used instead of 6 parts of PVA charged after the start of polymerization. was polymerized in the same manner as in Example 1 to obtain a polyvinyl acetate emulsion with a solid content concentration of 65.3% and a viscosity of 1700 mPas·s (30°C). The results of the initial adhesion of this emulsion are shown in Table 2.

【table】

Claims (1)

[Claims] 1 General formula R-S- () [where R represents an alkyl group having 1 to 20 carbon atoms which may have a hydroxyl group or a carboxyl group, and S represents a sulfur atom. ] Average degree of polymerization having a group represented by at one end 20~
An adhesive composition whose main component is a vinyl ester resin emulsion with 300 polyvinyl alcohol polymer as a protective colloid. 2. The adhesive composition according to claim 1, wherein the vinyl ester resin emulsion is a homopolymer of vinyl acetate or a copolymer emulsion of vinyl acetate and a polymerizable unsaturated compound. 3 The polymerizable unsaturated compound is ethylene and has 3 or more carbon atoms.
12. The adhesive composition according to claim 2, which is a vinyl ester or an acrylic ester. 4. The copolymer emulsion of vinyl acetate and a polymerizable unsaturated compound is an ethylene-vinyl acetate copolymer, and the ethylene content of the copolymer is 10 to 40 wt.
% of the adhesive composition according to claim 3. 5. The adhesive composition according to claim 1, wherein the solid content concentration of the vinyl ester resin emulsion is 55% or more.