JP2920302B2 - Stable cold crosslinking emulsion and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a synthetic resin aqueous emulsion in which a crosslinking reaction proceeds at room temperature after film formation. In the emulsion state, the crosslinking reaction does not proceed, and the minimum film forming temperature with time The present invention relates to a stable cold-crosslinkable emulsion which does not increase in water content and a method for producing the same.

[Prior Art] Conventionally, silane groups have room-temperature crosslinkability, and emulsions obtained by copolymerizing them have attracted particular attention as adhesives, binders for paints, binders for fiber processing, and the like.

It is widely known to produce a synthetic resin emulsion by emulsion-copolymerizing a polymerizable monomer having a silane group and another copolymerizable monomer, for example, Japanese Patent Publication No. 50-29952, `` Stable and Aggregated There are many inventions, such as "a method for producing an aqueous dispersion of a silanol group-containing polyvinyl ester containing no substance" and JP-B-62-61707, "Binder for Textile Processing".

However, in each of the prior arts, the amount of the polymerizable monomer having a silane group was 5% by weight or less based on all monomers.

Although there is an abstract description that the content is up to 40% by weight as a general concept, none of them is concrete, for example, it is not shown in Examples or Experimental Examples at all, and what kind of effect is obtained when 5% by weight or more is used. It is not entirely clear whether or not will be played.

[Problems to be Solved by the Invention] The present invention relates to a synthetic resin aqueous emulsion in which 6% by weight or more of a silane group having room temperature crosslinkability is introduced, and the cross-linking reaction proceeds at room temperature after film formation. The reaction does not proceed, and a stable cold crosslinking emulsion that exhibits a special effect that the minimum film forming temperature does not rise over time,
An object of the present invention is to provide a manufacturing method thereof.

[Means for Solving the Problems] The inventors of the present invention considered that if 6% by weight or more of the polymerizable monomer having a silane group is used, the crosslinking proceeds more, so that it is possible to obtain better film properties. I tried.

However, unexpectedly, when the amount of the polymerizable monomer having a silane group is 6% by weight or more, the film forming property of the synthetic resin emulsion decreases with time, and eventually a uniform and transparent film is not formed at room temperature. It was found that the expected properties of the film could not be obtained.

Regarding this cause, we have found that excess silane groups
This is thought to be because the cross-linking reaction occurs in the resin particles of the synthetic resin emulsion, causing incomplete fusion of the particles during film formation and increasing the minimum film forming temperature over time, thereby deteriorating the film forming properties. ing.

The present inventors have conducted various studies to solve this problem, and as a result, have found that this problem can be solved by an emulsion polymer having a specific composition range, and have completed the present invention.

That is, the present invention provides: “1. (A) one or more alkyl methacrylates having 4 or more alkyl groups, 94 to 70 parts by weight of polymerizable monomers having an alkoxysilane group. (C) A stable cold crosslinking emulsion obtained by emulsion polymerization of 0.1 to 5 parts by weight of one or more selected from acrylamide, N-methylolacrylamide, acrylic acid and sodium styrenesulfonate.

2. A part of (A) of the monomers described in claim 1 is replaced with 0.1 to 30 parts by weight of a total of one or more monomers of the following a, b, and c: A stable cold crosslinking emulsion obtained by emulsion polymerization.

A) water-insoluble monomer having no functional group copolymerizable with (A) 0 to 30 parts by weight b) water-insoluble monomer having any one of epoxy group, amino group and acetoacetyl group 0 to 10 parts by weight c Water-insoluble monomer having two or more polymerizable unsaturated groups 0 to 10 parts by weight 3. The monomer according to any one of claims 1 to 2 as an emulsifier A method for producing a stable cold-crosslinkable emulsion, characterized in that emulsion polymerization is carried out at a temperature of 60 ° C. or lower and at a pH of 5 to 8 using a redox catalyst in the presence of water. ".

According to the present invention, (A) an alkyl methacrylate having an alkyl group of 4 or more and one or more selected from (C) acrylamide, N-methylolacrylamide, acrylic acid, and sodium styrenesulfonate are used. (B) Even when 6% by weight or more of the polymerizable monomer having an alkoxysilane group is used, the resulting emulsion does not show any deterioration in film-forming properties over time, and is crosslinked at room temperature after film formation. The reaction proceeded, but the crosslinking reaction did not proceed in the emulsion state, and a stable cold crosslinking emulsion was obtained.

Examples of the alkyl methacrylate having an alkyl group having 4 or more carbon atoms include n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, stearyl methacrylate. Esters are preferred, and one or more selected from this group are used.

In the present invention, the alkoxysilane group is most suitable as the silane group, and the monomer having the alkoxysilane group is vinyltrimethoxysilane CH ₂ CHCHSi (OCH ₃ ) ₃ vinyltriethoxysilane CH ₂ CHCHSi (OC ₂ H ₅ ) ₃ vinyl tris (β-methoxyethoxy) silane CH ₂ CHCHSi (OC ₂ H ₄ OCH ₃ ) ₃ vinyl methyl dimethoxy silane γ-methacryloxypropyltrimethoxysilane CH ₂ ＣC (CH ₃ ) COO (CH ₂ ) ₃ Si (OCH ₃ ) ₃ γ-methacryloxypropylmethyldimethoxysilane γ-acryloxypropyltrimethoxysilane CH ₂ CHCHCOO (CH ₂ ) ₃ Si (OCH ₃ ) ₃ γ-acryloxypropylmethyldimethoxysilane γ-methacryloxypropyltriethoxysilane CH ₂ CHCH (CH ₃ ) COO (CH ₂ ) ₃ Si (OC ₂ H ₅ ) ₃ γ-methacryloxypropyltrimethyldiethoxysilane And one or a mixture of two or more selected from these groups can be used.

At least 6 parts by weight is required to exhibit room temperature cross-linking property. On the other hand, if it exceeds 30 parts by weight, a cross-linking reaction proceeds during polymerization and film forming properties are remarkably deteriorated.

In the present invention, as (C) to be copolymerized with (A) and (B), one or two selected from acrylamide N-methylolacrylamide acrylate sodium styrenesulfonate selected from water-soluble monomers. Use a mixture of more than one species.

The used amount is 0.1 to 5 parts by weight. If the amount is less than 0.1 part by weight, there is no effect. If the amount exceeds 5 parts by weight, the minimum film forming temperature with time increases remarkably.

With other water-soluble monomers, the minimum film-forming temperature rises over time, and a stable cold crosslinking emulsion cannot be obtained.

For example, when other water-soluble monomers such as methacrylic acid, methacrylamide, hydroxyethyl acrylate, hydroxyethyl methacrylate, and maleic acid are used, the minimum film formation temperature with time is significantly increased.

Further, in the present invention, a part of the monomer (A) is
It can be substituted with one or more of the monomers b and c.

(A) Examples of the water-insoluble monomer having no functional group other than the unsaturated group having copolymerizability with (A) include: alkyl methacrylate having 1 to 3 carbon atoms in the alkyl group, and acrylic acid. Acrylic esters such as methyl, ethyl acrylate, butyl acrylate and 2-ethylhexyl acrylate; vinyl esters such as vinyl acetate and vinyl propionate; acrylonitrile, styrene and 2,2,2 trifluoroethyl methacrylate; 2,3,3 tetrafluoropropyl methacrylate, 2- (perfluorooctyl) ethyl methacrylate, 2- (perfluorooctyl) ethyl acrylate, and the like.

 The amount used is 0 to 30 parts by weight.

(B) Examples of water-insoluble monomers having any one of functional groups of epoxy group, amino group, and acetoacetyl group include water-insoluble monomers having an epoxy group such as glycidyl methacrylate, and diethylaminoethyl methacrylate. There are water-insoluble monomers containing an amino group, and water-insoluble monomers containing an acetoacetyl group such as allyl acetoacetate and acetoacetoxyethyl methacrylate.

 The amount used is 0 to 10 parts by weight.

C. Examples of the water-insoluble monomer having two or more polymerizable unsaturated groups include divinylbenzene diallyl phthalate triallyl cyanurate triallyl isocyanurate tetraallyloxyethane and the like.

 The amount used is 0 to 10 parts by weight.

Next, the manufacturing method of the present invention will be described. In the emulsion polymerization method of the present invention, an appropriate emulsion polymerization means such as batch polymerization, monomer drop polymerization, and emulsion monomer drop polymerization can be used.

In particular, drop polymerization of an emulsion monomer is suitable for securing stability during production.

During the emulsion polymerization, it is necessary to suppress the reaction of the alkoxysilane group as much as possible, and it is preferable to carry out the polymerization at a temperature of 60 ° C. or lower using a redox catalyst and at a pH of 5 to 8.

Furthermore, when heavy metal ions are present in the emulsion polymerization system,
In order to promote the reaction of the hydrolyzable silyl group, it is preferable not to use those containing a heavy metal ion. A chelating agent such as disodium ethylenediaminetetraacetate may be used in combination.

Redox catalysts include ammonium persulfate, potassium persulfate and sodium acid sulfite, a combination of Rongalite, a combination of hydrogen peroxide and ascorbic acid, an organic peroxide (t-butyl hydroperoxide,
For example, a combination of benzoyl peroxide, cumene hydroperoxide, p-menthane hydroperoxide) with sodium acid sulfite, Rongalit, or the like is used. Particularly, a combination of an organic peroxide and a reducing agent is preferable.

[Action] As the polymerizable monomer having an alkoxysilane group is emulsion-copolymerized in water, it is difficult to completely suppress the reaction of the alkoxysilane group.

It is important to suppress the reaction of the alkoxysilane group as much as possible during emulsion polymerization, but for those containing a large amount of a polymerizable monomer having an alkoxysilane group of 6% by weight or more, stability after production is also important. .

In particular, as the reaction of the alkoxysilane group proceeds with time, the minimum film forming temperature of the copolymer increases, and a transparent and uniform film cannot be obtained.

In the present invention, a room temperature crosslinking emulsion which solves all of the above problems, is stable as an emulsion, and has stable film forming properties over time is provided.

The solution of these problems is achieved by using a specific monomer composition mainly containing an alkyl methacrylate having an alkyl group having 4 or more carbon atoms. Although the scientific elucidation of the reason is not yet sufficient, the present inventors believe that the suppression of hydrolysis of the alkoxysilane group is related to the hydrophobicity of the monomer composition.

There are still many unknown mechanisms why the alkoxysilane groups stable in the resin particles of the synthetic resin emulsion cause a crosslinking reaction in the film, but the film obtained from the cold-crosslinkable emulsion of the present invention has a After 10 days after drying, apparent film properties judged to be due to the crosslinking reaction of alkoxysilane groups, for example,
The improvement in performance such as a decrease in the solvent swelling ratio of the film is remarkable.

In addition, the coating obtained by adding a catalyst to this emulsion also shows a remarkable improvement in the physical properties of the coating.

This indicates that the alkoxysilane groups are stably present in the emulsion, and thus that the minimum film formation temperature is prevented from increasing over time.

However, the problems of stability in the production process during emulsion polymerization and mechanical stability of the emulsion are caused by the problem of the alkyl methacrylate having an alkyl group of 4 or more and the polymerizable monomer having an alkoxysilane group. It could not be solved only by copolymerization.

However, as a result of various studies, the present inventors have found that most of the water-soluble monomers raise the minimum film forming temperature with time as described above, but specific water-soluble monomers, that is, acrylamide, N -Methylol acrylamide, acrylic acid,
One or two selected from sodium styrenesulfonate
It has been found that the use of more than one species has a significant effect on solving this problem.

As a water-soluble monomer in the present invention, acrylamide,
The use of one or more selected from N-methylol acrylamide, acrylic acid, and sodium styrenesulfonate exhibits a special action and effect because they are combined with an alkyl methacrylate having an alkyl group having 4 or more carbon atoms. This is considered to be because the compatibility and copolymerizability of the polymer have an influence.

In other words, if the compatibility or copolymerization is different, the hydrophobic monomer separates into the inside of the particle and the water-soluble monomer separates into the particle surface during the process of forming the resin particles. As a result, there is little adverse effect that the hydrophilic group draws water into the inside of the particles, and an effect of obtaining a stable film-forming property without increasing the minimum film-forming temperature of the copolymer is exhibited.

In addition, the stability at the time of emulsion polymerization is remarkably improved by the aggregation of the hydrophilic groups on the surface of the resin particles, and the mechanical stability of the emulsion is also improved.

[Uses] The cold crosslinking emulsion of the present invention forms a silicone bond having a large binding energy by crosslinking, and forms a coating film having excellent durability and cold resistance. It is particularly useful as a binder for fibers, a binder for fiber processing, a binder for paper coating, a filler, and the like.

At the time of use, a known ultraviolet absorber and antioxidant may be added later.

In order to accelerate the curing of the coating film, a compound such as dibutyltin malate, para- or toluenesulfonic acid may be used as a catalyst.

 Next, the present invention will be described with reference to examples and comparative examples.

Example 1 n-butyl methacrylate 80 parts by weight γ-methacryloxypropyl tri 20 parts by weight methoxysilane acrylamide 2.5 parts by weight Polyoxyethylene nonylpheny 1 part by weight Ruthenium dodecylbenzenesulfonic acid sodium 1.4 parts by weight Water emulsification of 55 parts by weight A monomer composition was prepared, and then a polymerization catalyst consisting of 10 parts by weight of 10 parts by weight of t-butyl hydroperoxide and 10 parts by weight of a 3.5% aqueous solution of Rongalite was prepared.

40 parts by weight of water 0.3 parts by weight of ammonium acetate 1.3 parts by weight of polyoxyethylene nonylphenyl 1.3 parts by weight of sodium ether dodecylbenzenesulfonate To an emulsion polymerization apparatus charged with 0.7 parts by weight of the above-mentioned emulsion monomer composition,
Emulsion polymerization was started at 50 ° C. by adding 10% by weight and 30% by weight of the polymerization catalyst. 90% by weight of the emulsion monomer composition and 70% by weight of the polymerization catalyst were dropped in about 3 hours to carry out emulsion polymerization.
During the emulsion polymerization, the polymerization temperature was maintained at about 50 ° C, and the pH of the polymerization reaction solution was maintained.
Was maintained at pH 7 by appropriately adding a 5% by weight aqueous ammonia solution. After dropping, the mixture was aged for about 1 hour, and after cooling, the concentration was adjusted with an appropriate amount of water to obtain a stable cold crosslinking emulsion.

The obtained stable cold crosslinking emulsion had a concentration of 45% by weight, a pH of 7, and a minimum film formation temperature of 25 ° C.

The minimum film forming temperature is the lowest temperature at which a uniform and transparent film is formed when the emulsion is applied and dried, and the emulsion is applied and dried on a metal plate having a temperature gradient,
It is determined by measuring the lowest temperature at which a uniform, transparent film is formed.

Test Example For the cold-crosslinked emulsion obtained in Example 1, the stability of the emulsion was changed at the minimum film forming temperature, and
The following test was performed to determine the room temperature crosslinking property of the film by the solvent swelling ratio of the film. The test results are as shown in Table 1.

Change in minimum film formation temperature Place the room temperature crosslinking emulsion in a sealed container,
The change in the minimum film formation temperature after standing for a month and after standing at 70 ° C. for 2 days is measured.

The change in the minimum film forming temperature is less than 10 ° C.

Solvent swelling ratio of coating A cold crosslinking emulsion is applied to release paper and dried at room temperature to form a coating having a thickness of 100 μm. After forming the film, the film left at room temperature for 1 day and 10 days was immersed in toluene, and after 24 hours, the coefficient of linear expansion of the film was measured.

Also, 0.45 parts by weight of a crosslinking catalyst (dibutyltin malate) was added to 100 parts by weight of the normal temperature crosslinking type emulsion,
The mixture is stirred and mixed, applied to a release paper, and dried at room temperature to form a film containing a catalyst. After standing at room temperature for 1 day, the film was immersed in toluene and 24 hours later, the coefficient of linear expansion of the film was measured.

Examples 2 to 15 Emulsion polymerization was carried out in the same manner as in Example 1 except that the monomer composition of Example 1 was changed to the monomer composition shown in Table 1 to obtain a stable cold crosslinking emulsion.

 Its physical properties are as shown in Table 1.

In Examples 8 and 10, Texanol was added as a film-forming aid after polymerization.

Comparative Examples 1 to 9 Emulsion polymerization was carried out in the same manner as in Example 1 except that the composition of the monomer in Example 1 was changed to the monomer composition shown in Table 1.

In Comparative Examples 1 and 2, the emulsions obtained when one or two or more alkyl methacrylates having 4 or more carbon atoms in the alkyl group as the main monomer were not used had the lowest film forming temperature. , And a stable cold crosslinking emulsion could not be obtained.

Comparative Examples 3 and 4 are cases in which methacrylic acid and 2-hydroxyethyl methacrylate are used as hydrophilic monomers, and the resulting emulsion has a remarkable increase in minimum film forming temperature and obtains a stable cold crosslinking emulsion. I couldn't do that.

Comparative Example 5 was a case where methacrylamide was used as a hydrophilic monomer, and gelled during emulsion polymerization, and an emulsion could not be obtained.

Comparative Example 6 was a case where the amount of the polymerizable monomer having an alkoxysilane group was small, and the coating obtained from the emulsion was insufficient in room-temperature crosslinkability.

Comparative Example 7 gelled during emulsion polymerization when the amount of the polymerizable monomer having an alkoxysilane group was large, and an emulsion could not be obtained.

In Comparative Example 8, the amount of acrylic acid used was large. In the obtained emulsion, the minimum film-forming temperature was significantly increased, and a stable cold-crosslinking emulsion could not be obtained.

Comparative Example 9 was a case where the amount of acrylic acid used was small, and gelled during emulsion polymerization, and an emulsion could not be obtained.

Continuation of front page (56) References JP-A-60-181173 (JP, A) JP-A-3-21610 (JP, A) JP-A-57-6316 (JP, A) JP-A-58-157810 (JP) JP-A-62-119216 (JP, A) JP-A-61-221218 (JP, A) JP-A-60-81214 (JP, A) JP-A-59-202268 (JP, A) 62-61707 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) C08F 20/00-20/24 C08F 220/00-220/18 C08F 2/00-2/60 C08L 1 / 00-101/14 C09D 1/00-201/10

Claims (3)

(57) [Claims] (A) 94 to 70 parts by weight of (A) one or two or more alkyl methacrylates having alkyl groups of 4 or more (B) 6 to 30 parts by weight of a polymerizable monomer having an alkoxysilane group Part (C) One or more kinds selected from acrylamide, N-methylolacrylamide, acrylic acid, and sodium styrenesulfonate are emulsion-polymerized with 0.1 to 5 parts by weight of a stable cold crosslinking emulsion. 2. A part of (A) of the monomers described in claim 1 is 0.1 to 30 parts by weight in total of one or more of the following monomers (a), (b) and (c). Stable room temperature cross-linkable emulsion obtained by emulsion polymerization after replacing with. A) water-insoluble monomer having no functional group copolymerizable with (A) 0 to 30 parts by weight b) water-insoluble monomer having any one of epoxy group, amino group and acetoacetyl group 0 to 10 parts by weight C Water-insoluble monomer having two or more polymerizable unsaturated groups 0 to 10 parts by weight 3. Emulsion polymerization of the monomer according to claim 1 in the presence of an emulsifier and water at a temperature of 60 ° C. or lower and a pH of 5 to 8 using a redox catalyst. A method for producing a stable cold-crosslinked emulsion.