JPH0364528B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a crosslinked vinyl chloride copolymer. Vinyl chloride copolymers, which contain vinyl chloride and other polymerizable monomers as polymerization components, are widely used in applications where they are often dissolved in solvents, such as paints, adhesives, films, and fibers. There is. In order to be suitable for these uses, products with a relatively low degree of polymerization are often used to improve solvent solubility, but products with a low degree of polymerization have insufficient physical properties, so hydroxyl group-containing monomers are polymerized. It is known that the physical properties of vinylyl chloride resins can be improved by crosslinking them with isocyanates. However, in this method, it is practically necessary to add a low molecular weight compound such as triethylamine as a catalyst for the crosslinking reaction.
A drawback was that these low molecular weight catalysts oozed out onto the resin surface over time. The purpose of the present invention is to provide a method for producing a crosslinked vinyl chloride copolymer that does not require the use of the above-mentioned low molecular weight catalyst and does not bleed out. A copolymer solution is prepared by dissolving a vinyl chloride copolymer and an isocyanate compound in an organic liquid, and the organic liquid is substantially evaporated. system
A method for producing a crosslinked vinyl chloride copolymer characterized by maintaining the temperature at 30 to 150°C. The amount of vinyl chloride, which accounts for the majority of the copolymer in the present invention, is not particularly limited, but is usually 60 to 95% by weight. The vinyl chloride copolymer used in the present invention has a hydroxyl group-containing vinyl monomer and an acrylic tertiary amine as essential constituent units, of which the hydroxyl group-containing vinyl monomer component reacts with the isocyanate compound described below and crosslinks. It functions as a reactive group that forms a structure, and also exhibits properties unique to hydroxyl groups, such as adhesiveness, dyeability, hydrophilicity, compatibility with other resins, and pigment dispersibility. And as the above-mentioned hydroxyl group-containing vinyl monomer,
Examples of the former include those having a structural formula as a reaction product of acrylic acid or methacrylic acid and a polyhydric alcohol, and acrylic acid-based or methacrylic acid-based amides. Specific examples of the former include 2-hydroxyethyl (meth)acrylate (this represents both 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate (the same applies hereinafter), 2-hydroxypropyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate, polyethylene glycol represented by the following formula Mono(meth)acrylate _CH2 =CR-COO( _-CH2CH2O- ) _o H (n is an _integer from 2 to 9, R is hydrogen or methyl group), polypropylene glycol mono(meth) represented by the following formula
acrylate

[Formula] (n is an integer from 2 to 6, R is hydrogen or methyl group), 2-hydroxyethyl-2'-acryloyloxyphthalate A specific example of the latter is N-methylol (meth)acrylamide. These may be used alone or in appropriate combinations as constituent units of the copolymer, and 2-hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate are particularly preferably used. If the amount of the hydroxyl group-containing vinyl monomer used is too large, the copolymer's solubility in solvents may decrease, or its affinity with water may become too high, reducing the water resistance, which is a characteristic of vinyl chloride resins. If the amount is too small, the crosslinking reactivity will be poor and the crosslinking density will be low.
~30% by weight, preferably 2~20% by weight. The acrylic tertiary amine in the present invention refers to a tertiary amine containing an acryloyl group or a methacryloyl group, specifically (meth)acrylic acid esters such as dimethylaminoethyl (meth)acrylate and diethylaminoethyl (meth)acrylate. Suitable examples include dimethylacrylamide and dimethylacrylamide. The tertiary amine has the function of catalyzing the crosslinking reaction between the hydroxyl groups in the copolymer and the added isocyanate compound, and also has the function of well dispersing fine powder such as magnetic iron oxide powder. If this amount is too large, the speed of the crosslinking reaction between the copolymer and the isocyanate will be too high, resulting in problems such as a short pot life when used as a paint, making it impossible to put it to practical use. Generally, 0.05 to 5% by weight, preferably 0.1 to 5% by weight is added to the copolymer since the reaction rate tends to be low and a sufficient crosslinked structure cannot be obtained.
It is assumed to be 2% by weight. The vinyl chloride copolymer before crosslinking can be easily obtained by known polymerization methods such as solution polymerization and precipitation polymerization. In other words, in the former case,
A mixture of equal weights of methyl isobutyl ketone and toluene is used as a suitable solvent, and the resulting solution copolymer is used directly as a raw material for a binder after removing unreacted monomers, and the latter In this case, n-hexane is used as a suitable solvent and the copolymer is obtained as a fine powder. The degree of polymerization of the copolymer at this time is determined depending on the purpose of use, but in general, for applications such as paints where a large amount of pigment is added and applied thinly, a low degree of polymerization, for example 150 to 600, is used. In applications requiring mechanical strength, such as films or fibers, a high degree of polymerization, e.g.
1600 is appropriate. In the present invention, the isocyanate compounds used for crosslinking the vinyl chloride copolymer include tolylene diisocyanate, diphenylmethane diisocyanate, dianisidine diisocyanate,
Examples include tolidene diisocyanate, hexamethylene diisocyanate, metaxylylene diisocyanate, and a reaction product of 1 mol of trimethylolpropane and 3 mol of tolylene diisocyanate.
It is commercially available from Co., Ltd. under the trade name "Coronate L." The amount of the isocyanate compound to be used is usually 0.3 to 30 parts by weight per 100 parts by weight of the copolymer, since the final coating film will become brittle if it is too large. In order to obtain a crosslinked vinyl chloride copolymer by the method of the present invention, the vinyl chloride copolymer before crosslinking is mixed with a suitable organic liquid such as toluene, methyl ethyl ketone, methyl butyl ketone, isopropyl alcohol, cyclohexanone, benzene, acetone, After dissolving them alone or in a mixture of two or more, adding pigments, stabilizers, modifiers, etc. as necessary and mixing well, usually add isocyanate at the end and mix further, and immediately After evaporating the above-mentioned organic liquid through the final process such as application to the base material, film formation, and spinning,
It is heated to a temperature of 150°C, preferably 40-130°C. The organic liquid in the above copolymer solution may be evaporated at room temperature or by heating, but if the temperature is too high after the organic liquid has evaporated and dried, the copolymer will decompose and hydrogen chloride will be released. Inconveniences such as detachment may occur,
If the temperature is too low, the crosslinking reaction of the copolymer will not be promoted, so it is necessary to maintain the temperature at 30 to 150°C. The method of the present invention is configured as described above, and prepares a copolymer solution in which a vinyl chloride copolymer and an isocyanate compound are dissolved in an organic liquid,
According to the present invention, the acrylic tertiary amine component in the copolymer is heated at an appropriate temperature, and the organic liquid is maintained at a temperature of 30 to 150°C in a state where the organic liquid is substantially evaporated. It has a catalytic effect that promotes the crosslinking reaction between the hydroxyl group-containing vinyl monomer component and the isocyanate compound, and a vinyl chloride copolymer with a high crosslinking density can be easily obtained. It does not ooze out over time. The present invention will be explained below with reference to Examples. Example 1 A stainless steel autoclave with an internal volume of 4 and equipped with a stirrer was charged with 900 g of a mixed solution of methyl isobutyl ketone and toluene (weight ratio 1:1) and 6 g of isobutyl peroxide, and then the air inside the autoclave was removed. Next, a monomer mixture consisting of vinyl chloride, 2-hydroxypropyl acrylate and dimethylaminoethyl acrylate was charged into the jacket of the autoclave while cooling the autoclave by passing cooling water at 20 DEG C. while stirring. After that, hot water was passed through the jacket and heated until the internal temperature reached 32°C to start the polymerization reaction, and then the temperature of the reaction system was lowered to 32°C.
It was maintained at ℃. After carrying out the above polymerization reaction for 4 hours, the reaction system was heated again for 20 hours.
It was cooled to .degree. C., and unreacted vinyl chloride was removed by blowing nitrogen gas from the bottom to obtain a solution-like copolymer.
The amounts of vinyl chloride, 2-hydroxypropyl acrylate, and dimethylaminoethyl acrylate were 860 g, 78 g, and 4.5 g, respectively. The resulting copolymer solution was precipitated with n-hexane, washed, and then dried at 50° C. for 24 hours to obtain 390 g of a slightly yellow powdered copolymer A. The resin A had a degree of polymerization of 280 and had a composition of 78.9% vinyl chloride, 20.1% 2-hydroxypropyl acrylate, and 1.1% dimethylaminoethyl acrylate. Next, copolymer A was dissolved in a mixture of toluene and methyl isobutyl ketone (weight ratio 1:1) to prepare a 15% copolymer solution, and then an isocyanate compound (Japan Polyurethane Industries Co., Ltd. To the vinyl chloride copolymer, 0.65 parts of Coronate L) was added and stirred until homogeneous. Furthermore, a part of it was placed on a smooth glass plate with a film thickness of 0.1.
mm, and left at room temperature for 24 hours to remove most of the solvent, then dried in a vacuum dryer for 24 hours while heating at 50℃ to create a transparent film. When the fraction and heat adhesion were measured, the former was 85% by weight, and the latter was judged as ○.
(Does not adhere). On the other hand, the speed of the crosslinking reaction in the solution state was measured using a B-type viscometer by holding a part of the solution at 20°C and measuring the increase in viscosity of this solution. It was as shown in Table 1. The gel fraction is determined by the weight of the vinyl chloride copolymer film obtained as described above after immersing it in a mixed solvent of toluene and methyl isobutyl ketone (weight ratio 1:1) at 50°C overnight. This is the value (% by weight) divided by the weight of the film before immersion, and serves as a guideline for determining the reaction efficiency of the crosslinking reaction between the copolymer and the isocyanate compound. In addition, the heat adhesion of the above copolymer film is 120
This test was conducted to see whether or not the magnetic layers adhered to each other when heated at a temperature of 15 minutes (°C).In the table, ○ means no adhesion (blocking does not occur), and × means adhesion. shows. Example 2 Polymerization was carried out according to Example 1 using the same equipment and the same monomers as those used in Example 1. However, the amount of each monomer charged was slightly changed and the polymerization was carried out in n-hexane. After the polymerization reaction is complete, unreacted vinyl chloride is removed by blowing nitrogen gas from the bottom, and the copolymer is extracted in a slurry state and purified by repeated filtration and washing with n-hexane, followed by drying at 50°C for 24 hours. A powdered copolymer B was obtained. The composition of copolymer B was as shown in Table 1. In the same manner as copolymer B, copolymers C, D and E having the compositions shown in Table 1 were obtained. Next, for each of copolymers B to E, Example 1
In the same manner as above, a copolymer solution was prepared, an isocyanate compound was added thereto to prepare a film, and the gel fraction, heat adhesion, and solution viscosity were measured, and the results were as shown in Table 1. In this example, after removing most of the solvent from the isocyanate compound-added copolymer solution, the solution was dried in a vacuum dryer for 24 hours while heating at 50°C to create a transparent film. The heating time after the partial solvent is removed is appropriately selected depending on the heating temperature and the amount of tertiary amine in the copolymer, and is generally 2 minutes or more.

[Table] Comparative Example A binary copolymer of vinyl chloride and 2-hydroxypropyl acrylate (2-hydroxypropyl acrylate component, 20% by weight) with a polymerization degree of 560 was produced in the same manner as in Example 2, and an isocyanate compound was added. After that, the viscosity increase of the solution and the film properties were measured. The results showed that the gel fraction was 12%, the heat adhesion was judged as x, and no increase in the viscosity of the solution was observed, indicating that almost no crosslinking reaction had occurred.

Claims (1)

[Scope of Claims] 1. A copolymer solution is prepared by dissolving a vinyl chloride copolymer having a hydroxyl group-containing vinyl monomer and an acrylic tertiary amine as constituent units and an isocyanate compound in an organic liquid, A method for producing a crosslinked vinyl chloride copolymer, which comprises maintaining the system at a temperature of 30 to 150°C while the organic liquid is substantially evaporated. 2. The first, which maintains the system at a temperature of 40 to 130℃
Manufacturing method described in section.