JPS62167377A - Method for preventing skin-forming of aqueous emulsion type tackifier - Google Patents

Abstract

PURPOSE:To prevent skin-forming phenomena, a drawback of aqueous emulsion type tackifier, effectively and to improve adhesiveness characteristics of aqueous pressure-sensitive adhesive, by blending the aqueous emulsion type tackifier with a water-soluble salt of casein as a skin-forming inhibitor. CONSTITUTION:(A) 100pts.wt. (solid content) aqueous emulsion type tackifier comprising rosin and/or rosin derivative (e.g., at least one consisting of fumarated rosin, maleinized rosin, rosin ester, maleinized rosin ester and fumarated rosin ester, having 70-140 deg.C softening point) as a dispersed phase and water as continuous phase is blended with (B) 0.1-5pts.wt. water-soluble salt of casein to provide skin-forming prevention properties without lowering adhesiveness of characteristic aqueous emulsion type pressure-sensitive adhesive.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for preventing skinning of an aqueous emulsion type tackifier.

[Prior Art] Conventionally, water-based adhesives include natural rubber latex, styrene-butadiene rubber latex (hereinafter referred to as SBR latex), carboxylated styrene-butadiene rubber latex (hereinafter referred to as carboxylated SBR latex), and acrylic. Products made by mixing emulsions (hereinafter referred to as latexes) with emulsions of rosin and/or rosin derivatives (hereinafter referred to as resin emulsions) are known. It is coated on various base materials and used to manufacture labels, PVC tapes, etc.

Recently, water-based adhesives tend to have higher concentrations due to demands for energy and labor savings, and therefore, it is necessary to increase the concentration of emulsion-type tackifiers that are constituent components of the water-based adhesives. However, when the solid content concentration of the tackifier is increased (35% or more), the tackifier is hydrophobic and has a high softening point, so it dries extremely quickly, resulting in emulsion-type tackification during storage and transportation. The disadvantage is that a skinning phenomenon occurs on the surface of the agent. For this reason, a method is adopted in which the skin layer produced by the filtration operation is removed before or after the compounding of latex and resin emulsions. It cannot be removed and may cause problems as described below. In other words, if the water-based adhesive contains a skinned material, it will be difficult to apply it uniformly to the various substrates mentioned above, which will reduce the commercial value and quality of the resulting PVC tape. This will result in a decrease in

In order to solve these problems, various anti-skinning agents have been studied in the past, but their effects may be insufficient, or even if they are effective, the surface performance of the emulsion-type tackifier is insufficient. However, it has the disadvantage of decreasing adhesion, water resistance, emulsion stability, etc.

[Problems to be Solved by the Invention] The present invention solves problems that could not be solved by the prior art, namely, the effects of various known anti-skinning agents are insufficient,
In view of the fact that even if the emulsion-type tackifier is effective, it has the disadvantage of degrading its original performance, we have conducted intensive studies to find a new and effective anti-skinning agent.
It was discovered that the above-mentioned problems could be solved by using casein, a well-known protein, as a water-soluble salt as a dispersant, and the invention was completed based on this new knowledge.

[Means for Solving the Problems] The present invention provides an aqueous emulsion type tackifier in which rosin and/or a rosin derivative is a dispersed phase and water is a continuous phase, based on 100 parts by weight of the solid content of the tackifier. The solid content of casein water-soluble salt is 0.1 to 0.1 as an anti-skinning agent.
The present invention relates to a method for preventing skinning of an aqueous emulsion type tackifier, which comprises mixing 5 parts by weight of an aqueous emulsion type tackifier.

[Example] In the present invention, natural rubber latex, SBR latex, and carboxylated SBR latex can each be used alone, but in terms of the balance of various properties such as adhesive strength, tack, and cohesive force, these latexes can be used in combination. It is preferable that the solid content ratio is natural rubber latex/natural rubber latex/weight ratio.
The SBR latex is preferably 20,780 to 50,150.

The SBR latex used here preferably has a styrene content of 20 to 40% by weight ff1%.

In the present invention, rosin includes natural rosin, hydrogenated rosin, disproportionated rosin, and perhydrated rosin, and rosin derivatives include esterified products of these rosins or partially fumarized or maleated rosins. Examples include those obtained by esterifying the fumaride or the maleate, and these usually have a softening point of 70 to 140°C. The alcohols used in the esterified product are not particularly limited, and include glycerin, trimethylolpropane, trimethylolethane, 1.2.8-hexanetriol, 1.2.4-butanetriol, pentaerythritol, etc. Various types can be used.

The resin emulsion used in the present invention is obtained by adding an anionic emulsifier, a nonionic emulsifier, an anionic-nonionic emulsifier, etc. to the rosin or an esterified product of the rosin and emulsifying the rosin. The amount used is 0.5 to 10% based on the solid content of the resin emulsion.
The amount is preferably 1 to 5% by weight.

If it is less than 0.5ffiff1%, the stability of the resin emulsion will deteriorate, and if it exceeds 10% by weight, the water resistance of the resulting adhesive will deteriorate, which is not preferable. As the emulsification method, any of so-called inversion emulsification, forced emulsification, and self-emulsification may be employed.

In addition, in the present invention, in order to achieve the objective of effectively preventing skinning of the aqueous emulsion type tackifier,
It is essential to add casein water-soluble salt. Here, casein is a natural phosphoprotein, and in the present invention, both formal and soybean products can be used. A water-soluble casein salt is obtained by solubilizing casein in an aqueous solution of a basic substance. Examples of the basic substance include sodium hydroxide, potassium hydroxide, ammonia, and organic amines, and these substances can be used alone or in combination, but ammonia is most suitable when considering the water resistance of the resulting adhesive. be. The amount of the basic substance to be used is not particularly limited and may be used in an amount sufficient to make casein a water-soluble salt. For example, in the case of 28% ammonia water, it is 5 to 20% by weight based on casein. It is better to

The amount of the water-soluble casein salt added is preferably 0.1 to 5 parts by weight, preferably 0.5 to 2 parts by weight, based on 100 parts by weight of the solid content of the resin emulsion. Further, upon addition, the solid content concentration of the casein water-soluble salt is not particularly limited, but it may normally be added as an aqueous solution having a solid content concentration of 10 to 15%. If the amount added is less than 0.1 parts by weight, the anti-skinning property of the resulting adhesive will be insufficient, and if it is added in excess of 5 parts by weight, the initial adhesiveness will be reduced. This is not desirable. The aqueous emulsion type tackifier of the present invention thus obtained can be suitably used as an aqueous adhesive by mixing it with the latexes in a specific ratio. The mixing ratio is 100 parts by weight of the latex in terms of solid content and 50 to 50 parts by weight of the aqueous emulsion type tackifier in terms of solid content.
The amount is preferably 150 parts by weight. If the amount of the tackifier is less than 50 parts by weight, the adhesive strength tends to decrease, and if it exceeds 150 parts by weight, the cohesive force tends to decrease, so neither is suitable.

That is, the water-based adhesive of the present invention not only has good anti-skinning properties, but also exhibits excellent adhesion when used in combination with the latexes in the proportions described above. That is, the addition of water-soluble caseinate effectively prevents the adhesive from forming a skin, and also further improves the inherent adhesive properties of the adhesive.

Hereinafter, the present invention will be explained in detail with reference to Production Examples, Examples, and Comparative Examples, but the present invention is not limited to these. In each example, all parts and percentages are based on weight unless otherwise specified.

Production Example 1 100 parts of glycerin ester (softening point: 100°C) and 60 parts of toluene were heated with stirring to form a toluene varnish, and then 3 parts of sodium dodecylbenzenesulfonate and 160 parts of water were added as emulsifiers to pre-emulsify. Then, forced emulsification was performed at 70°C and 300 kg/cm to obtain an emulsion. Further, the emulsion was heated at 50°C under reduced pressure (80~
Detoluenization and concentration are performed with 120 mm/1 g),
A resin emulsion having a solid content of 50%, a pH of 3.5, and a viscosity of 50 cP was obtained.

Production Example 2 In Production Example 1, partially fumarated rosin pentaerythritol ester (
Production was carried out in the same manner as in Production Example 1, except that a softening point (softening point: 125°C) was used.
OAP resin emulsion was obtained.

Example 1 30 parts of natural rubber latex (in terms of solid content), 70 parts of SBR latex with a styrene content of 40% (in terms of solid content),
99 parts of the emulsion obtained in Production Example 1 (solid content equivalent)
and 1 part of casein-ammonia aqueous solution (solid content equivalent)
were mixed to prepare a water-based adhesive with a solid content of 50%.

(Measurement of adhesive strength) Add a small amount of acrylic thickener to the adhesive and
After adjusting the viscosity to cP, apply it to a primer-treated soft PVC sheet so that the glue thickness after drying is 40 items.
It was dried for 3 minutes in a circulating air dryer set at ℃ to produce a PVC tape.

Attach the PVC tape to a soft PVC sheet at room temperature,
After aging for 2 hours in drying room 4 at 0°C,
After being left in a constant temperature room adjusted to 65% humidity for 2 hours, the vinyl chloride tape was peeled off and replaced with a stainless steel plate, and 30 minutes later, the adhesive strength was measured at a peeling speed of 300 mm/min.

(Measurement of anti-skinning property) 1 part of casein-ammonia aqueous solution (in terms of solid content) was added to 99 parts of the resin emulsion obtained in Production Example 1 (in terms of solid content).
Add 100g of the mixture to a 140ml mayonnaise bottle, seal it tightly, and soak it in a 40°C water bath for 10 minutes.
The stopper was opened and the container was left in a hot water bath, and the time required for skin to form was measured.

Examples 2 to 4 and Comparative Examples 1 to 2 In Example 1, at least one of the type of resin emulsion used, the amount used, and the amount of casein-ammonia aqueous solution used was changed as shown in Table 1. , prepared in the same manner as in Example 1, with a solid content of 50
% of various water-based adhesives were obtained.

The adhesive strength of these various water-based adhesives was evaluated in the same manner as in Example 1.

In addition, the anti-skinning property was evaluated by changing at least one of the type of resin emulsion used, the amount thereof used, and the amount of the casein-ammonia aqueous solution used in the method for evaluating anti-skinning property of Example 1 as shown in Table 1. Other than that,
Various preparations were prepared in the same manner as in Example 1 and evaluated in the same manner.

Comparative Example 3 Adhesion and anti-skinning properties were evaluated in the same manner as in Example 3, except that polyvinyl alcohol (manufactured by Kuraray ■, trade name: Poval 205) was used instead of the casein-ammonia aqueous solution. did.

Comparative Example 4 Adhesive strength and anti-skinning properties were tested in the same manner as in Example 3, except that polyethylene glycol (manufactured by Sanyo Chemical Industries, Ltd., trade name: PEG100OO) was used in place of the casein-ammonia aqueous solution. evaluated.

Comparative Example 5 Adhesion and anti-skinning properties were evaluated in the same manner as in Example 3, except that sodium polyacrylate was used instead of the casein-ammonia aqueous solution.

The results obtained in Examples 1 to 4 and Comparative Examples 1 to 5 were
Shown in the table.

[Margin below] Table 1 The results obtained in Examples 1 to 4 and Comparative Examples 1 to 5 are shown in Table 2.
Shown in the table.

Table 2 [Effects of the Invention] According to the method for preventing skinning of an aqueous emulsion type tackifier of the present invention, the skinning phenomenon, which is a drawback of highly concentrated aqueous emulsion type tackifiers made of rosin and/or rosin derivatives, can be prevented. Since it has the effect of effectively preventing the occurrence of the tackifier and improving the tiW properties of the tackifier, it has the effect of further improving the adhesive properties of the resulting water-based adhesive.

Patent applicant: Arakawa Chemical Industry Co., Ltd. Hi-P practitioner'

Claims (1)

[Scope of Claims] 1. In an aqueous emulsion type tackifier in which rosin and/or rosin derivative is a dispersed phase and water is a continuous phase, as an anti-skinning agent based on 100 parts by weight of the solid content of the tackifier. A method for preventing skinning of an aqueous emulsion type tackifier, which comprises mixing 0.1 to 5 parts by weight of casein water-soluble salt as a solid content. 2. The rosin derivative serving as the dispersed phase is at least one selected from fumarated rosin, maleated rosin, rosin ester, maleated rosin ester, and fumarated rosin ester, and has a softening point of 70 to 140°C. A method for preventing skin formation according to claim 1.