JPS5815518B2 - Aqueous dispersion for pressure sensitive materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to aqueous dispersions which, when dried, give highly tacky elastomers.

It is well known that diene polymers in general, and natural rubber in particular, are widely used as components of cavity pressure materials. Generally speaking, a release agent is applied to one side of a film such as cellulose or polyester, or kraft paper, etc. It is manufactured by applying one layer of primer on the other side and then applying a pressure sensitive layer.

The pressure-sensitive layer is made of natural rubber that has been masticated and broken down with a roll, etc., and is made into a solvent solution of about 20mm diameter, and a tackifier (tackifier) such as terpene resin, rosin-based resin, or petroleum resin is added to this. -) is added in approximately the same amount as rubber.

After coating this pressure-sensitive layer stock solution on the first layer of primer,
The solvent is recovered by evaporation.

As can be seen from this process, the use of solvents in the preparation of the pressure-sensitive layer stock solution and the recovery of the solvent poses problems such as deterioration of the working environment, danger, and pollution during recovery, so pressure-sensitive layers that do not use organic solvents are recommended. The emergence of methods for preparing layers is desired.

From this point of view, emulsifying the tackifier itself and blending the emulsion with natural rubber latex may be promising as a means to solve the above problems.

However, it has been found that the operation of forming fine particles of the tackifier into an aqueous emulsion is surprisingly complicated, and even if the mixture is mixed with natural rubber latex or the like and then dried, it is difficult to form a uniform film.

Surprisingly, the inventors have found that if aqueous dispersions of diene-based polymers and copolymers meet certain conditions;
It was discovered that an excellent pressure-sensitive material can be obtained, and the present invention was developed.

That is, conjugated diene (capital) ~], OO weight ratio saturated carboxylic acid 0 to 10 weight ratio and other polymerization components 50
The aqueous dispersion of the present invention contains, as particles of the aqueous dispersion, a polymer having a gel content of 0 to 60, a gel swelling degree of 30 or more, and an intrinsic viscosity of the toluene soluble portion of 0.9 or less. When dried and the water evaporated, it exhibits excellent tackiness and is extremely useful as a pressure-sensitive material.

In the present invention, the polymer made of the above-mentioned polymeric components will be hereinafter simply referred to as a "polymer", and the solid obtained by removing water from the aqueous dispersion will be referred to as an "elastic body".

In the present invention, when the content of conjugated diene in the polymer is less than 50%, the tackiness of the elastic body obtained from the aqueous dispersion decreases.

The content of the polymerization component is more preferably 60φ or more.

Isoprene is the best conjugated diene, but butadiene, chloroprene, 2,3-dimethylbutadiene, etc. can also be used.

When the conjugated diene is butadiene or chloroprene, the tackiness is insufficient, so it is necessary to make sure that there is substantially no gel in the polymer, and even if it exists, the degree of swelling is 50 or more, and that toluene is not allowed. It is preferable that the intrinsic viscosity of the melted part be 0.7 or less from the viewpoint of the adhesiveness of the elastic body obtained from the dispersion of the present invention.

The unsaturated carboxylic acid component does not necessarily need to be present in the polymer used in the present invention, but from the viewpoint of the stability of the aqueous dispersion and the tackiness of the resulting elastic body, it is limited to 10% by weight. In many cases, it is preferable that the unsaturated carboxylic acid contains preferably 5 weight percent or less.

Unsaturated carboxylic acids include monobasic acids such as acrylic acid, methacrylic acid, and maleic acid monoalkyl esters that can be copolymerized with conjugated dienes, and dibasic acids such as maleic acid, fumaric acid, and itaconic acid, either singly or in combination. It can be used as

Furthermore, the polymer used in the present invention may contain polymerization components other than those mentioned above, if desired.

This is useful when considering compatibility when blending the polymer with other substances.

However, if the amount of other polymerized components exceeds 50% by weight, the adhesiveness of the elastic body often decreases markedly.

The amount of other polymer components in the polymer is preferably 40 weight or less when the glass transition temperature of the polymer consisting only of the polymer components exceeds 808C.

In that case, the most preferred amount is 30 weight or less.

Other polymeric components include, for example, styrene, substituted styrene, (
Methyl acrylate, ethyl (meth)acrylate,
(meth)propyl acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, (meth)acrylate
2-hydroxyethyl acrylate, (meth)acrylonitrile, etc. can be used.

The polymer used in the present invention may be in a form in which a conjugated diene, an unsaturated carboxylic acid, and other polymer components are bonded in a so-called random manner, or, for example, a part of a conjugated diene and an unsaturated carboxylic acid may be copolymerized. It may also be a mixture of the remaining conjugated diene and other polymerization components copolymerized.

That is, the bonding mode of these polymer components does not particularly matter.

In the present invention, it is desirable that no gel exists in the polymer, but its presence to some extent is allowed depending on the properties of the gel and the amount of gel.

In addition, in the present invention, the gel content is defined as 1 g of polymer added to 200 cc of toluene, kept at 30°C for 24 hours, filtered through a glass filter (No. 3), dried and weighed the filtered polymer. However, it is expressed as a proportion to the original polymer.

The degree of swelling of the gel is expressed as the ratio of the weight of the swollen gel to the polymer separated during the gel content measurement described above, and this indicates the properties of the gel □.

If the gel content of the polymer measured in this manner exceeds 60, the adhesive force of the elastic body is low.

Generally, the gel content is preferably 40% or less.

Even if the gel content is within the range specified by the present invention, if the swelling degree of the gel is 30 or less, the adhesive strength of the elastic body will decrease.

The degree of swelling of the gel is preferably 50 or more.

Furthermore, it is an important condition in the present invention that the intrinsic viscosity of the toluene-soluble portion of the polymer is 0.9 or less.

If the intrinsic viscosity of the toluene soluble portion exceeds 0.9,
The adhesive strength of the elastic body decreases markedly.

The lower the intrinsic viscosity of the toluene-soluble portion, the greater the adhesive force of the elastic body, so from this point of view, the intrinsic viscosity is preferably 0.6 or less.

Note that the intrinsic viscosity is measured using toluene as a solvent and a 5-point dilution method at a temperature of 30°C.

The concentration of the polymer in the aqueous dispersion of the present invention is not particularly limited, but is usually in the range of 20 to 70 φ.

Aqueous dispersions can be produced by dissolving (or partially swelling) a previously prepared polymer in a solvent, emulsifying it in water in the presence of an emulsifier, etc., and removing the solvent. It is better to carry out emulsion polymerization of the above polymerization components using a radical polymerization initiator in the presence of an emulsifier and, if necessary, to remove any residual additives from the system for reasons such as controlling the polymer particle size or its distribution. So, it's preferable.

The particle diameter of the polymer is generally suitable to be in the range of 0.05 to 1 μm.

Known polymerization means can be applied to the preparation of the polymer.

The aqueous dispersion of the present invention contains antioxidants, metal oxides,
It may also contain metal hydroxides, salts, etc.

□ The dispersion of the present invention does not substantially contain an organic solvent, and the elastic body obtained by removing water is extremely sticky, so it cannot be used in itself or other polymeric materials or An aqueous dispersion for pressure-sensitive materials is prepared by mixing inorganic materials and the like.

Note that the dispersion can also be widely used as adhesives, coating materials, paints, and the like.

Furthermore, since the polymer in the dispersion of the present invention contains a conjugated diene, it can be vulcanized if desired.

In this case, for example, by adding colloidal sulfur to the dispersion of the present invention, the so-called initial tack is excellent, and the permanent adhesive strength can also be increased by subsequent vulcanization.

The present invention will be explained in more detail below using Examples.

Parts in the examples mean parts by weight. Example 1 98 parts of isoprene and 2 parts of methacrylic acid were emulsified in 150 parts of water in the presence of 5 parts of polyoxyethylene nonyl phenyl ether sulfate, and 2 parts of n-dodecyl mercaptan and 0.5 parts of sodium sulfate were added. After replacing the inside with nitrogen,
The temperature was raised to 70°C.

An aqueous solution containing 1 part of potassium persulfate, which had been replaced with nitrogen, was added to the system to initiate polymerization.

When the polymerization rate reached 99% after a polymerization time of 23 hours, the mixture was cooled to room temperature.

The resulting aqueous dispersion had a viscosity of 80 centivoids, a solids content of 42, and a particle size (as measured by an electron microscope after fixation with osmic acid) of about 0.09 μm.

A portion of this aqueous dispersion was added to a 20% aqueous sodium sulfate solution, and the coagulated polymer was thoroughly washed with water and then dried at room temperature under reduced pressure.

When we measured the gel content, swelling degree of the gel, and intrinsic viscosity of the soluble part using a part of the polymer using toluene as a solvent, the results were 47%, 42, and 0.82 dl/, respectively! 7
Met.

A film was prepared by pouring a portion of this aqueous dispersion into a glass dish and volatilizing the water at 50°C.

The film was sticky. Example 2 In place of the polymerization components of Example 1, 1 part of acrylic acid, 75 parts of isoprene, and 24 parts of styrene were used, and 2 parts of polyoxyethylene nonylphenyl ether sulfate and 3 parts of sodium dodecylbenzenesulfonate were used as emulsifiers. , the amount of water was 110 parts, and the polymerization component mixture was divided into 3 parts to 5 parts.
Polymerization was carried out in the same manner as in Example 1, except that the mixture was added to the system at intervals.

After 23 hours, the polymerization rate became 95φ. By heating the reaction system and reducing the pressure slightly, unreacted polymerized components are expelled.
An aqueous dispersion was obtained.

Analyzing in the same manner, the gel content was 25, the swelling degree of the gel was 57, and the intrinsic viscosity of the soluble portion was 0.75 dl/g.

The adhesive strength of the film produced on the glass plate was slightly greater than that of Example 11.

Examples 3 to 7 Various aqueous dispersions were prepared in the same manner as in Example 1 or Example 2.

Table 1 summarizes the composition, properties, and tackiness of these polymers.

In addition, those outside the scope of the present invention are also shown as comparative examples.

As is clear from Table 1, it is an essential condition for the film to exhibit adhesiveness that the gel content, swelling degree of the gel, and intrinsic viscosity of the soluble part are all within the ranges defined by the present invention. It is.

It is also clear that the use of butadiene as the conjugated diene tends to reduce the tackiness of the film.

Claims (1)

[Claims] 1 Consists of a conjugated diene of 50 to 100 parts by weight, an unsaturated carbonic acid of O to 10 parts by weight, and other polymerization components of 50 parts by weight or less, a gel content of O to 60 parts, a gel swelling degree of 30 or more, and a toluene soluble part. An aqueous dispersion for a pressure-sensitive material, comprising a polymer having an intrinsic viscosity of 0.9 or less as particles of the aqueous dispersion.