JPH0780975B2 - Method for producing α-methylstyrene copolymer for ceramic binder - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing an α-methylstyrene copolymer suitable as a ceramic binder. More specifically, it relates to a method for producing an α-methylstyrene copolymer which is preferably used when a film- or sheet-shaped ceramic molded article is produced by a doctor blade method or a calendar method.

[Prior Art] Various molding methods are known for manufacturing ceramic products, but binders of various organic polymer compounds are used for manufacturing relatively precise structures. There is. As a binder, it is easy to form a ceramic structure before sintering, and the structure has some strength,
In addition, the binder smoothly decomposes and scatters during sintering,
It is required that binders and decomposed products thereof do not remain in the sintered ceramic structure. For this reason, conventionally, polymethacrylic acid ester-based and polystyrene-based resins having relatively good thermal decomposability are required. Is widely used.

[Problems to be Solved by the Invention] Poly-α-methylstyrene-based resins are extremely excellent in thermal decomposability, but they are relatively poor in compatibility with ceramic powder, and poly-α-methylstyrene-based resins are When a ceramic structure is made by using it as a binder, the structure is brittle, and there is a problem that it is impossible to wind the formed product, especially when making a sheet-shaped or film-shaped ceramic molded product.

In order to solve the above problems, it is considered that α-methylstyrene is copolymerized with a polar group-containing monomer such as dialkyl acrylamide, acrylic acid or methacrylic acid, and further a monomer such as butyl methacrylate or butyl acrylate. However, α-methylstyrene needs to undergo anionic polymerization in order to obtain a high polymer,
The conventional method has a problem that a copolymer cannot be obtained with the above polar group-containing monomer, butyl methacrylate and butyl acrylate.

[Means for Solving the Problem] The present inventor diligently studied a method for solving the above problem, found a method for producing an α-methylstyrene copolymer suitable for a ceramic binder, and completed the present invention.

That is, the method for producing an α-methylstyrene copolymer for a ceramic binder according to the present invention uses α-methylstyrene and α using an anionic polymerization initiator in the presence of a hydrocarbon solvent.
-The sum of the monomers shown below for methylstyrene is
Copolymerizing N, N-dialkylacrylamide with acrylic acid and / or methacrylic acid in an amount of 0.05 weight ratio or less, and then α
It is characterized in that butyl methacrylate and / or butyl acrylate in an amount of 0.1% by weight or more and 1.0% by weight or less of methylstyrene is added to carry out the polymerization reaction.

In the present invention, it is possible to replace a part of α-methylstyrene with styrene or a nuclear-substituted derivative thereof, and the ratio thereof is preferably less than 30% by weight of α-methylstyrene, and above that. Poor thermal decomposition.

N, N-dialkyl used in the present invention (wherein the alkyl is lower alkyl having 1 to 5 carbon atoms, preferably methyl or ethyl). Acrylamide and acrylic acid and / or methacrylic acid are in a weight ratio of α-methylstyrene of 0.05. It is below, preferably 0.001 to 0.03 weight ratio. When it is more than 0.05 weight ratio, the easily decomposable property of poly α-methylstyrene is lost, which is not preferable. On the other hand, when it is less than 0.001 weight ratio, the compatibility with ceramics is insufficiently improved, which is not preferable.

In the present invention, the amount of butyl methacrylate and / or butyl acrylate is not less than 0.1 weight ratio and not more than 1.0 weight ratio of α-methylstyrene. If the amount is less than 0.1% by weight, the improvement in the fragility of the structure is small, while if it is more than 1.0% by weight, the thermal decomposition property of poly α-methylstyrene is lost, which is not preferable.

As the anionic polymerization initiator used in the present invention, organolithium is preferably used, and among them, alkyllithium, specifically, n-butyllithium, sec-butyllithium and the like are mentioned as commercially available. The amount used is not particularly limited, and an appropriate amount is selected depending on the composition of copolymerization and the molecular weight.

In the present invention, as the activator, ethylene glycol dialkyl ether, diethylene glycol dialkyl ether, or ethers such as tetrahydrofuran can be used.

In the present invention, as the polymerization medium, a hydrocarbon solvent, preferably α-methylstyrene itself or an inert solvent such as benzene, toluene, ethylbenzene, hexane, heptane, methylcyclohexane, decalin or tetralin can be used.

In the present invention, the temperature for copolymerizing α-methylstyrene and N, N-dialkylacrylamide and acrylic acid and / or methacrylic acid is not particularly limited, but substantially unreacted monomers are present. It is preferable to carry out at a low temperature, at which the composition of the obtained copolymer can be quantitatively determined. The polymerization temperature for that is usually 5 ° C or lower,
-5 ° C to -50 ° C is preferably used.

Further, the present invention is characterized in that α-methylstyrene, N, N-dialkylacrylamide, acrylic acid and / or methacrylic acid are copolymerized, and then butyl methacrylate and / or butyl acrylate are added to carry out the copolymerization reaction. . The addition rate is not particularly limited, but it is preferably such that the addition does not generate heat, and the polymerization temperature in this polymerization is also relatively low, usually 5 ° C. or lower.

There is no limitation on the polymerization time in each copolymerization, but several minutes to several tens hours are suitable depending on the desired monomer conversion rate and the polymerization temperature.

After the completion of the polymerization reaction, it is treated with an anionic polymerization deactivator (alcohols, water, epoxy compound, etc.), and then an inert solvent is distilled off if necessary, steam distillation or thrown into a large amount of methanol. It is also possible to separate the copolymer by sedimentation.

[Effects of the Invention] By carrying out the method of the present invention, it is possible to obtain a thermally decomposable copolymer for forming a ceramic structure that is well compatible with a ceramic powder suitable for a ceramic binder and has good moldability, It is extremely valuable industrially.

[Examples] The present invention is further described below with reference to Examples.

Example 1 35 ml of α-methylstyrene, 100 ml of toluene, 0.5 ml of diethylene glycol dimethyl ether, 0.5 ml of N, N-dimethylacrylamide and 0.1 ml of methacrylic acid were added, and n-butyllithium was added at room temperature until coloring by living polymer was observed. After coloring was observed, 1 mmol was further added, and the temperature was adjusted to -5 ° C to carry out polymerization for 2 hours. To the α-methylstyrene living polymer solution, 15 ml of n-butyl methacrylate was added in about 3 minutes, polymerization was carried out at −5 ° C. for 2 hours, and then 1 ml of methanol was added to deactivate. The weight of the dried copolymer obtained by throwing it into a large amount of methanol was 42 g. The contents of N, N-dimethylacrylamide, methacrylic acid and n-butylmethacrylate are 1.1 each.
%, 0.2% and 31.6% by weight, and the intrinsic viscosity in a toluene solution at 30 ° C. was 0.48. The softening point of the obtained polymer was 125 ° C.

Comparative Example 1 No polymer was obtained when polymerization was carried out under the same conditions as in Example 1 except that n-butyl methacrylate was charged at the same time as α-methylstyrene.

Example 2 An experiment was conducted in the same manner as in Example 1 except that 15 ml of iso-butyl methacrylate was used instead of 15 ml of n-butyl methacrylate. The polymer yield was 94% by weight based on the total monomers, the intrinsic viscosity was 0.45, and the contents of N, N-dimethylacrylamide, methacrylic acid and iso-butylmethacrylate were 1.0% by weight, 0.2% by weight and 31.8% by weight, respectively. Met. The softening point of the obtained polymer was 130 ° C.

Comparative Example 2 The same experiment as in Example 1 was carried out except that 15 ml of n-butyl methacrylate was not added. The softening point of the obtained polymer is 230.
It was ℃.

Test Example 10 g of each of the copolymers of Examples 1 and 2 was dissolved in 30 ml of toluene and kneaded with 30 g of alumina (particle size: 2 μm), and both were well dispersed to form a uniform slurry. Further, after removing the solvent, this structure could be molded at 80 ° C. or higher.

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Claims (3)

[Claims] 1. An α-methylstyrene in the presence of a hydrocarbon solvent and α-methylstyrene, and the total amount of the following monomers based on α-methylstyrene is 0.05% by weight or less N,
Copolymerization of N-dialkyl acrylamide with acrylic acid and / or methacrylic acid followed by α-methylstyrene
A method for producing an α-methylstyrene copolymer for a ceramic binder, comprising adding butyl methacrylate and / or butyl acrylate in an amount of 0.1 to 1.0 by weight to carry out a polymerization reaction. 2. The production of α-methylstyrene copolymer for a ceramic binder according to claim 1, wherein the polymerization reaction is carried out at a low temperature at which substantially no unreacted monomer is present. Method. 3. The method for producing an α-methylstyrene copolymer for a ceramic binder according to claim 1, wherein the polymerization reaction is carried out at 5 ° C. or lower.