JPH0453891A - Production of aqueous emulsion type pressure-sensitive adhesive - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention is directed to adhesiveness to various adherends and moisture deterioration resistance when coated paper is used as a surface substrate. The present invention relates to a method for producing an aqueous emulsion type adhesive with excellent properties.

(Prior art) Conventionally, organic solvents such as aromatics, esters, and ketones, which have excellent adhesive properties, coating suitability, drying properties, and water resistance, have been used as adhesives. So-called solution-type adhesives were the mainstay. However, in recent years, water-based emulsion type adhesives have attracted attention due to their resource saving, non-pollution, and safety and health aspects.In particular, the market share of water-based emulsion type adhesives mainly composed of polyacrylic acid alkyl ester copolymers is increasing year by year. are doing.

Water-based emulsion type adhesives are used for tapes.

General labels, frozen food labels, stickers, stickers,
There are products for business forms, etc., and the material of the object to be adhered to is as follows:
plastic, metal, glass, paper.

It covers a wide range of fields, including a 9-tier ceramic pole case.

In particular, the demand for plastic products continues to increase, and the proportion of polyolefin resins in particular is safe.

It is gradually increasing in terms of hygiene, cost, and functionality.

- Boat fishing (2. Water-based emulsion adhesives tend to be inferior to solution-based adhesives in terms of water resistance, moisture resistance, adhesion, drying properties, and stability, especially polyolefin-based adhesives. There are two requirements for adhesive strength to the object to be adhered to.

On the other hand, in recent years, the number of types of surface substrates for adhesive coatings has increased, and in particular, the number of coated paper substrates that swell, such as cast coated paper and coated paper, has increased. . When an adhesive coated product using these coated papers as the surface base material and coated with a water-based emulsion type adhesive is left in a high temperature and high humidity environment, the adhesive strength and physical properties of the tank are significantly reduced ( (hereinafter referred to as humidity deterioration resistance).

Conventionally, methods for improving adhesion to various adherends,
Regarding methods for improving humidity deterioration resistance, there are literatures on each method, and there are no reports on improvement measures that solve these problems at the same time. In other words, as for the method of improving adhesion to various adherends, it is possible to mix polyvinyl acetate-based resins that have structural characteristics through multi-stage polymerization, such as two-stage polymerization or three-stage polymerization, and There are many methods of mixing rosin-based resins with tackifiers such as oil-based resins, and there are no methods for improving moisture deterioration resistance.

On the other hand, regarding humidity deterioration resistance, the addition of a sequestrant for metal ions to suppress metal crosslinking between metal ions contained in the paper base material and carboxyl groups in the adhesive is being considered. (Japanese Unexamined Patent Publication No. 63-2288.4), is this method effective for moisture deterioration resistance, and is it effective for adhesion to polyolefin-based objects and rough surfaces such as cardboard? However, it has the disadvantage that the adhesive strength is low, and it is not a means to improve the adhesiveness and humidity deterioration resistance in a well-balanced manner.

(Problem to be solved by the invention) The present invention improves the various drawbacks mentioned above, and improves the adhesion to various adherends and the resistance to moisture deterioration when coated paper is used as the surface substrate. The present invention provides a method for producing an excellent aqueous emulsion type adhesive.

[Structure of the invention]

(Means for Solving the Problems) The present invention contains an acrylic acid alkyl ester having an alkyl group having 4 to 12 carbon atoms as a main component, and α.

When obtaining an aqueous emulsion type adhesive by emulsion polymerization of a monomer containing 0.5 to 5% by weight of β-ethylenically unsaturated carboxylic acid, up to 40% by weight of the α,β-ethylenically unsaturated carboxylic acid 5 of the monomer mixture which may contain an amount of
0 to 99.8% by weight is emulsion polymerized to produce an aqueous emulsion, and then the above α,β-
This is a method for producing an aqueous emulsion-type adhesive by emulsion polymerizing the remaining amount of ethylenically unsaturated carboxylic acid alone or as a mixture with other monomers.

The aqueous emulsion type adhesive of the present invention is an emulsion of an acrylic resin containing an acrylic acid alkyl ester as a main component. Carbon number 4-1 used in acrylic resin
As the acrylic ester having 2 alkyl groups,
Examples include acrylic esters of linear or branched fatty acid alcohols such as butyl acrylate, hexyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, dendritic acrylate, and lauryl acrylate. A combination of two or more types is also permissible. These acrylic esters account for 60 to 99.5% by weight of the total amount of monomers forming the acrylic resin. Preferably 70-90% by weight
use. Examples of α,β-ethylenically unsaturated carboxylic acids include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, and fumaric acid.

In addition to the above monomers, the acrylic resin of the present invention includes hydroxyl group-containing acrylic esters such as β-hydroxyethyl acrylate, β-hydroxypropyl acrylate, β-hydroxyethyl methacrylate, and β-hydroxypropyl methacrylate. Or methacrylic acid ester,
acrylamide and N-methylolacrylamide,
Acrylic acid alkyl esters having an alkyl group of 3 or less carbon atoms, such as acrylamide derivatives such as N-butoxymethylacrylamide, methyl acrylate, ethyl acrylate, and propyl acrylate;
It can be obtained by copolymerizing four monomers such as methacrylic acid ester, vinyl acetate, styrene, and acrylonitrile.

The emulsion type adhesive of the present invention is obtained by emulsion polymerization. In the first example, emulsion polymerization is carried out by continuously dropping a monomer mixture containing a polymerization initiator into water containing an emulsifier. At this time, first, α,β-ethylenically unsaturated carboxylic acid is added in an amount of 0 to 40% by weight based on the amount used. Preferably 10-40
Emulsion polymerization is carried out using a monomer mixture of % by weight. The monomers emulsion polymerized at this stage account for 50% of the total monomer amount.
It is at least 80% by weight, more preferably at least 90% by weight, and the upper limit is 99.8% by weight. The α,β-ethylenically unsaturated carboxylic acid may not be used, or it is preferable to include it in order to balance humidity deterioration resistance and holding power.

stomach.

The remaining amount of the α,β-ethylenically unsaturated carboxylic acid is then added dropwise, either alone or as a mixture with other monomers, to continue the emulsion polymerization. The emulsifier may be contained in the water to be dropped, or may be contained in the form of a pre-emulsion together with the monomer mixture.

Examples of emulsifiers include polyoxyethylene alkylphenol ether sulfate or sulfonate, alkylhensensulfonate, α-olefin sulfonate, and the like, used alone or in combination with polyoxyethylene alkylphenol ether and polyoxyethylene stearate.

A polyoxyethylene-polyoxypropylene block copolymer or the like may be used.

As a polymerization initiator, persulfates such as ammonium persulfate, potassium persulfate, and sodium persulfate are used.

Peroxides such as persulfuric acid, hydrogen peroxide, and cumene hydroperoxide are used, and in some cases, these are combined with reducing agents such as sodium thiosulfate, ersorbic acid, and ferrous ammonium sulfate to perform a redox reaction. It can also be polymerized with

It is also possible to use polymerization regulators of mercaptans such as dodecyl mercaptan and, if necessary, water-soluble salts as buffers.

The present invention focuses on the method of adding α,β-ethylenically unsaturated carboxylic acid during emulsion polymerization, and the present invention focuses on the method of adding α,β-ethylenically unsaturated carboxylic acid during emulsion polymerization.
is added in the latter half of polymerization. The emulsion pressure-sensitive adhesive obtained in this way shows good results in adhesion to various objects and moisture deterioration resistance when coated paper is used as the surface substrate. The α,β-ethylenically unsaturated carboxylic acid component is an indispensable component in the composition of the pressure-sensitive adhesive, and at the same time it makes a very large contribution to various required physical properties. Regarding the adhesive strength to polyolefin-based objects, it is preferable that the amount of α,β-ethylenically unsaturated carboxylic acid component is small in terms of polarity.
Regarding the adhesion strength to corrugated holes, etc., the higher the better, as long as the holding power is not reduced. In addition, regarding the cutting suitability required for post-processing of the coated product and the adhesive cutting property when punching out labels and stickers, it is preferable that the adhesive has a high holding power. It is necessary to introduce a large amount of unsaturated carboxylic acid component. However, when coated paper is used as the surface substrate, the humidity deterioration resistance is α,
The quality becomes poor in inverse proportion to the amount of β-ethylenically unsaturated carboxylic acid component introduced. As described above, it is not possible to satisfy various required physical properties by considering only the type and amount of the α,β-ethylenically unsaturated carboxylic acid monomer.

The method of adding α,β-ethylenically unsaturated carboxylic acid is to add it directly to the reaction vessel. Any method may be used.

In the aqueous emulsion type adhesive of the present invention, the emulsion components include portions with a large amount of carboxylic acid and portions with a small amount of carboxylic acid, and an emulsion having a wide polarity distribution can be obtained.

As a result, the wettability to various objects to be adhered to was well balanced over a wide range, and it is thought that the adhesion to polyolefin-based objects in particular was greatly improved. In addition, regarding humidity deterioration resistance, regarding the reactivity with metal ions in the coated paper base material, there are areas with a lot of carboxylic acid that preferentially react with metal ions, and areas with a small amount of carboxylic acid that are less likely to react with metal ions. coexist, and reactions occur selectively in areas with a large amount of carboxylic acid.As a result, when looking at the physical properties of the adhesive as a whole, the rate of deterioration is lower than that of an emulsion synthesized by uniform dropping, and the adhesive coating is It is thought that the moisture deterioration resistance of the structure has improved.

The present invention will be explained below with reference to Examples. In steel, "part" means part by weight, and "%" means percent by weight.

Example 1 250 parts of ion-exchanged water, 2 parts of polyoxyethylene alkylphenol ether, and 2 parts of ammonium sulfate salt of polyoxyethylene alkylphenol ether were charged into a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a dropping funnel, without stirring. When the temperature is raised to 80°C, 1 part of ammonium persulfate is added, and the previously emulsified pre-emulsion shown below is added dropwise.

2-ethylhexyl acrylate 790 parts Hinyl oxalate 70 parts Methyl methacrylate 80 parts 2-hydroxyethyl methacrylate 30 parts Methacrylic acid
6 parts polyoxyethylene alkylphenol ether 13 parts ammonium sulfate salt of polyoxyethylene alkylphenol ether 13 parts ion-exchanged water 441 parts ammonium persulfate 4 parts The temperature inside the reaction vessel was maintained at 80° C. and added dropwise over 3 hours. Simultaneously with the completion of the dropwise addition, 24 parts of methacrylic acid is added to the reaction vessel. Thereafter, 1 part of ammonium persulfate is added twice every hour to complete the polymerization.

The resulting milky white emulsion had a solid content of 60%, pH 3,
0, and the viscosity was 1500 cps (BL viscometer, #30-ter 30 rpm).

Add preservatives, antifoaming agents, aqueous ammonia, and thickeners to this emulsion to achieve a viscosity of 15,000 to 20,000 cps.
(BL viscometer, #40-tar, 12 rpm) was obtained.

This aqueous emulsion type adhesive was coated on a commercially available polyethylene laminated paper separator at a dry weight of 20 to 25 g/', dried at 100°C for 2 minutes, and then reversed onto a commercially available cast coated paper to prepare a coated product. This coated product is J l5-Z
-0237, adhesive strength, holding power, etc. were measured. The coated product left at 23°C-6596 is called the normal coated product.
The coated product was left in a high temperature and high humidity atmosphere at 50°C-9896 for 2 days and then left at 23°C at 65% for 1 day as a humidified aged coating. Humidity deterioration resistance was evaluated using the adhesive force value of the object as the retention rate of physical properties over time under humidification. In other words, the closer this value is to 100%,
The lower the humidity deterioration resistance is and the closer it is to 096, the higher the humidity deterioration resistance is.

Example 2 Into the same reaction pot as in Example 1, 250 parts of ion-exchanged water, 2 parts of polyoxyethylene alkylphenol ether, and 2 parts of ammonium sulfate salt of polyoxyethylene alkylphenol ether were charged, and when the temperature reached 80°C with stirring, 1 part of ammonium persulfate was added. The following pre-emulsion, which had been emulsified by adding 30% of the pre-emulsion, was added dropwise.

2-ethylhexyl acrylate 790 parts Hinyl acetate 70 parts Methyl methacrylate 80 parts 2-hydroxyethyl methacrylate 30 parts Methacrylic acid
6 parts polyoxyethylene alkylphenol ether 13 parts ammonium sulfate salt of polyoxyethylene alkylphenol ether 13 parts ion-exchanged water 441 parts ammonium persulfate 4 parts The temperature in the reaction vessel was raised to 80'
I kept it at C for 3 hours.

dripped. After dropping 82 parts by weight of all the monomers constituting the emulsion, 24 parts of methacrylic acid is added into the pre-emulsion, mixed and dropped. Thereafter, ammonium persulfate is added twice, 1 part per hour, to complete the polymerization.

The resulting milky white water-based adhesive emulsion had a solid content of 5.
9.8'% pH 3.0 viscosity 1650 cps.

Example 3 In the same recipe as in Example 2, 82% by weight of the total monomers constituting the emulsion was added dropwise, and then 82% by weight of methacrylic acid was added.
1 part to the reaction kettle at once. Thereafter, 8 parts of methacrylic acid was intermittently added to the reaction vessel after 15 minutes had elapsed, and 8 parts of methacrylic acid had been added intermittently to the reaction vessel after 30 minutes had elapsed (at the end of the dropwise addition).

Then add 2 parts of ammonium persulfate every hour.
2 times to complete the polymerization.

The resulting milky white water-based adhesive emulsion had a solid content of 5.
9.996 pH 3.1 Viscosity 1780 cps.

Comparative Example 1 The raw material composition and quantity were the same as in Example 1, or 30 parts of methacrylic acid was mixed with other monomers and added dropwise.

Example 4 An aqueous emulsion was obtained in the same manner as in Example 1. However, the monomer composition to be added dropwise first is as follows.

Butyl acrylate 640 parts Lauryl acrylate 200 parts Ethyl acrylate 100 parts Methacrylic acid 2
Hydroquine ethyl 40 parts acrylic acid
4 parts Then, after the completion of the dropwise addition of the monofouling mixture described above, 16 parts of acrylic acid was added at once, and the following operations were the same as in Example 1.

The resulting milky white water-based adhesive emulsion had a solid content of 5.
9.8% pH 2.5 viscosity 1200 cps.

Example 5 An aqueous emulsion was obtained in the same manner as in Example 1. However, the monomer composition to be added dropwise first is as follows.

2 Ethylhexyl acrylate 729 parts Hinyl acetate 135 parts Methacrylic acid 5 parts Next, after completing the dropwise addition of the monomer mixture listed in L, a monomer mixture having the following composition was added dropwise, and the operation after the completion of the dropping was the same as in Example 1.

2-ethylhexyl acrylate 81 parts Vinyl acetate 15 parts Methacrylic acid 35 parts The obtained milky white aqueous emulsion for adhesive had a solid content of 59.796 p.
H3, 3 jo degree 1900 CpS was there.

Each Example and Comparative Example was prepared into an aqueous emulsion type adhesive in the same manner as in Example 1.

In addition, a coated product was created using the same processing method.

〔Effect of the invention〕

According to the present invention, it has become possible to obtain an aqueous emulsion-type pressure-sensitive adhesive that has excellent adhesion to various objects to be adhered to and excellent moisture deterioration resistance when coated paper is used as the surface substrate.

Claims (1)

[Claims] 1. Aqueous emulsion type produced by emulsion polymerization of monomers containing acrylic acid alkyl ester having an alkyl group having 4 to 12 carbon atoms and 0.5 to 5% by weight of α,β-ethylenically unsaturated carboxylic acid. 50 to 99.8% by weight of the monomer mixture which may contain up to 40% by weight of the α,β-ethylenically unsaturated carboxylic acid mentioned above to obtain the adhesive.
is emulsion-polymerized to produce an aqueous emulsion, and then the remaining amount of the α,β-ethylenically unsaturated carboxylic acid is emulsion-polymerized in the presence of the emulsion, either alone or as a mixture with other monomers. A method for producing an aqueous emulsion type adhesive.