CS261256B1 - Solution acrylic binders for ceramic films and method for their preparation - Google Patents

Abstract

The polymer component of the binder is a copolymer of alkyl esters of acrylic acid, alkyl esters of methacrylic acid and optionally functional acrylic monomers from the group including acrylic and methacrylic acid and their amides optionally substituted on nitrogen with methylol, alkyl or alkoxymethyl groups, hydroxyalkyl esters and glycidyl esters. Solution binders are prepared by 2 to 3-phase radical polymerization of a mixture of monomers in organic solvents, in such a way that the first phase of polymerization is carried out at a lower temperature and with a lower solvent content and in each subsequent phase the polymerization temperature and/or solvent content is increased.

Description

The invention relates to solution acrylic binders suitable for the preparation of ceramic films intended for lamination and subsequent production of ceramic multilayer structures and for the preparation of ceramic films for the production of substrate, surface dielectrics and other flat ceramic products.

These products are usually prepared by cutting ceramic fiber foil in which the cohesion of the individual particles of the inorganic filler ensures appropriate macromolecules! binder. Although this binder acts only temporarily as a reinforcing agent for the basic ceramic powder, it has to meet a number of important technological requirements. In the first stage of production, the binder is required to allow complete homogenization of the casting composition and to achieve the hydrodynamic properties needed to process the composition on the casting machine. The solvent system must not attack the casting machine support and must ensure that the film is dried in the required technological time. Macromolecules! the binder component must ensure the consistency of the particles of powdered ceramic material and give the film the necessary technological properties, in particular strength and flexibility, and allow the stamping or cutting of the desired surface shapes, their further treatment and lamination. in a new casting compound. At the final stage of the process, the binder must be quantitatively removed from the system by firing at high temperatures without causing undue deformation or other damage to the products. The volume contraction that occurs when the products are fired should be kept to a minimum. The binder component of the ceramic film casting composition (typically a solution of a thermoplastic polymer in volatile organic solvents. In order to achieve the necessary mechanical properties of the film, the binder system may also contain plasticizers, an overview of suitable polymers is given in US Pat. No. 2,966,719. They use various cellulose derivatives, polyvinyl butyral (US pt. 4,104,345) and copolymers prepared by block or solution polymerization of acrylic monomers, but these materials usually do not make it possible to obtain sufficiently homogeneous and integrated ceramic films with a minimum of pores and minimum volumetric firing contractions.

[0007] The present invention, on the one hand, provides a solution of acrylic binders for ceramic films containing 40 to 65% by weight. % organic solvents, up to 60 wt. % of acrylic copolymers and optionally up to 10 wt. plasticizers and, secondly, their preparation process by 2 to 3 phase free radical polymerization of a mixture of monomers in organic solvents in the presence of polymerization initiators. The binder comprises an acrylic copolymer having a polydispersity greater than 4, prepared by 2 to 3 phase free-radical copolymerization of a monomer mixture consisting of 30 to 90% by weight. % alkyl esters of acrylic acid having a carbon number of 2 to 8, 10 to 80 wt. % alkyl esters of methacrylic acid having a number of carbon atoms in the alkyl group of 1 to 8 and optionally up to 8 wt. functional acrylic monomers selected from the group consisting of acrylic and methacrylic acid, its amides optionally substituted on nitrogen by methyl, alkyl or alkoxymethyl groups having from 1 to 5 carbon atoms and hydroxyalkyl esters having from 2 to 4 hydroxyalkyl groups and glyoidyl esters thereof. The process for preparing these acrylic binders is characterized in that the first stage of polymerization is conducted at a temperature of at least 53 ° C and a solvent content of 20 to 40% by weight in the reaction mixture. and at each subsequent stage, the polymerization temperature and / or solvent content of the reaction mixture is increased such that the last polymerization stage is carried out at a temperature of 70 ° C to the boiling point of the reaction mixture and having a solvent content of 40-65% by weight.

The solution acrylic binders of the present invention have a number of advantages over other polymeric binders for ceramic films. First of all, they contain in the polymer chain both segments of soft alkyl esters of acrylic acid as well as segments of hard alkyl esters of methacrylic acid, enabling to obtain the ceramic foil of the necessary mechanical properties. By preparing the binder by stepwise polymerization, the resulting copolymer is characterized by a non-standard and wide molecular weight distribution, which both contributes significantly to the balance of mechanical and other application properties of the ceramic film and enables homogeneous and highly integrated film to be obtained. firing.

The acrylic and methacrylic acid esters of aliphatic alcohols except tertiary, with a maximum of 8 carbon atoms, such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, 3-pentanol , n-hexanol, 1-methylpentanol, 2-methylpentanol, 2-ethylbutanol, 3-methylpentanol, n-heptanol, 1-methylhexanol, 2-methylhexanol, 3-methylhexanol, 3-heptanol, 2-ethylpentanol, n-octanol, isooctanol , 2-hydroxyethanol. The copolymer component can also be carboxylic, hydroxyl, amide or oxirane functional acrylic monomers, either individually or in any combination, but not more than 8% by weight. in a mixture of all monomers. Of the carboxyl group-containing monomers, acrylic acid and methacrylic acid are used in the present invention. Holders of the hydroxyl group are hydroxyalkyl-c derivatives of acrylic and methacrylic acid having a carbon number of 2-4 in the alkyl group, in particular 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 4- hydroxybutyl methacrylate. Among the monomers containing amide groups, acrylamide, methacrylamide, methylolamides of acrylic acid and methacrylic acid, methylolamides of these acids etherified with C 1 -C 4 alcohols, and optionally N-alkyl substituted C 1 -C 5 -alkyl methacrylamides in the alkyl substituent are used. Of the oxirane-containing monomers, glycidyl acrylate and glycidyl methacrylate are suitable.

Organic solvents which comprise 40 to 65 wt. The solution of acrylic binder according to the invention is chosen according to the requirements of the binder production technology and its application.

From a technology point of view, the transfer constants, solubility and boiling points must be taken into account when selecting solvents. The chain transfer may suitably affect the molecular weight of the polymer being formed at some stage of the polymerization and hence the width distribution of the resulting polymeric binder component. Aromatic hydrocarbons (e.g. toluene, xylene, ethylbenzene), esters (e.g. ethyl acetate, propyl acetate, n-butyl acetate, isobutyl acetate), ketones (e.g. acetone, methyl ethyl ketone, methylisobutyl ketone), ethers (e.g. tetrahydrofuran), aliphatic alcohols (e.g. ethanol, n-propanol, isopropanol, n-butanol, isobutanol) and others. Aliphatic solvents boiling up to 110 ° C may be used to a limited extent. Hexane is suitable, for example.

The other component of the solution acrylic binder of the present invention may be up to 8 wt. plasticizers added to increase the flexibility of the ceramic film. Among the organic plasticizers, phthalic acid esters with aliphatic alcohols having more than 4 carbon atoms are particularly recommended for this purpose, such as n-butanol, isobutanol, 3-pentanol, n-hexanol

1-methylpentanol, 2-methylpentanol, 2-ethylbutanol, 3-methylpentanol, n-heptanol, 1-methylhexanol,

2-methylhexanol, 3-methylhexanol, 3-hepfanol, 2-ethylpentanol, n-octanol, isooctanol, 2-ethylhexanol and others.

The preparation of the solution alkyl binder according to the invention is carried out by a 2 to 3 phase polymerization of a mixture of acrylic monomers with an initiator in organic solvents, the temperature or solvent content of the reaction mixture or both being increased gradually in the individual stages of preparation. The initiator may also be added in other stages of the preparation either together with the solvents to be added or separately to complete the polymerization, but up to a maximum of 3% by weight. to monomers. The polymerization is generally initiated at a temperature of 55 + 2 ° C in all or part of the prescribed solvents. This low temperature, or even a limited amount of solvents, creates conditions for the formation of long macromolecular chains. The resulting copolymer is characterized by a high molecular weight with a classical molecular weight distribution. In subsequent phases, the polymerization conditions change in favor of the formation of short macromolecular chains, both by stepwise increasing the temperature, but not more than the boiling point of the reaction mixture, and by adding other solvents, thereby significantly reducing the concentration of reacting monomers. In these phases, up to 2 other copolymers are produced chemically identical to the polymer of the first production stage, but with a substantially lower molecular weight and generally higher polydispersity. The result of this dilution. The polymerization process is 2 to 3 chemically identical copolymers, differing in particular by the average molecular weight values in which the molecular weight distributions interpenetrate, so that the macromolecular component of the product acts as a single polymer with a broad molecular weight distribution.

As polymerization initiators, organic peroxides, hydroperoxides, peracid esters or diazo compounds are used, such as dibenzoyl peroxide, di-tert-butyl peroxide, tert-butyl hydroperoxide, dicumyl peroxide, cumene hydroperoxide, tert-butyl perbenzoate, azo-bis-isobutyronitrile. azo-bis-2,4-dimethylvaleronitrile and the like, which are usually added in an amount of 0.1 to 30% by weight based on the monomer content. However, other radical polymerization initiators may also be used.

The composition of solution acrylic binders for ceramic films and the process for their preparation are exemplified by the following examples.

He did

60 wt. parts of butyl acrylate, 40 wt. parts by weight of methyl methacrylate, 4 wt. parts by weight of acrylic acid and 0.3 wt. % of dibenzoyl peroxide is polymerized in a mixture of organic solvents consisting of 40 wt. parts of n-butanol and 30 wt. of xylene at 70 to 72 ° C. After 3 hours, 90 wt. parts of n-butyl acetate and polymerization is continued at 70-72 ° C. Three hours after the addition of n-butyl acetate, the temperature is raised to the boiling point of the mixture at which the polymerization is complete for 6 hours, two portions of cumene hydroperoxide at 0.3% by weight being added at two hour intervals. to the amount of monomers.

The prepared acrylic binder has a viscosity of 3 to 6 Pa.s at 25 ° C, a non-volatile content of 38 to 40% by weight. The polymer component has a glass transition temperature of about -10 ° C and a polydispersity of 4.4 to 5.2.

Example 2

80 wt. parts by weight of ethyl acrylate, 20 wt. parts of methyl methacrylate and 0.25 wt. At 55-57 ° C, a portion of 2,2'-azo-bis-isobutyronitrile was polymerized in a 64 wt. parts of ethyl acetate. The polymerization is carried out under an inert nitrogen atmosphere until the solution has a viscosity of 4 to 6.5 Pa.s. At this point, 82 wt. parts of toluene and continue the polylemination at 55 to 57 ° C until a viscosity of 8 to 12 Pa.s. The nitrogen is then discontinued and the mixture is heated to the boiling point at which the reaction is complete for 6 hours. Finally, 8 wt. parts of dibutyl phthalate.

The prepared acrylic binder prepared has a viscosity of 25 to 35 Pa.s at 25 ° C, a non-volatile content of 41 to 43% by weight. The polymer component has a glass transition temperature of about -4 ° C and a polydispersity greater than 5.

Example 3

40 wt. parts by weight of 2-ethylhexyl acrylate, 33 wt. parts by weight of butyl methacrylate, 27 wt. parts by weight of methyl methacrylate, 2 wt. 0.2 parts by weight of methacrylic acid; of glycidyl methacrylate and 9.4 wt. % of azo-bis-2,4-dimethylvaleronitrile in a mixture of 30 wt. parts of isopropanol and 30 wt. parts of ethyl acetate are subjected to polymerization under an inert nitrogen atmosphere at a temperature of 54 to 57 ° C. The polymerization in the first phase lasted 5 hours, then the nitrogen feed was stopped and the temperature was raised to 70-74 ° C. At this temperature, the polymerization was completed for 6 hours, with 2 portions of tert-butyl hydroperoxide in a total amount of 0.4% by weight at 2 hour intervals. to the amount of monomers. At the end, 11 wt. parts hexane and 6 wt. parts of diisoctyl phthalate.

The prepared acrylic binder prepared has a viscosity at 25 ° C in the range of 4 to 8 Pa.s, a non-volatile content of 56 to 60% by weight. The polymer component has a glass transition temperature of about -4 ° C and a polydispersity of 4.5 to 5.8.

Example 4

35 wt. parts by weight of ethyl acrylate, 65 wt. % of butyl methacrylate and 0.55 wt. % of the dibenzoyl peroxide is polymerized in a mixture of organic solvents consisting of 50 wt. parts of n-butanol and 20 wt. of toluene at 65-70 ° C. At this temperature the polymerization proceeds until the product has a viscosity of 1.5 to 2.5 Pa.s. 30 wt. parts of isobutyl acetate and polymerization was continued at 65-70 ° C for 4 hours. In the final phase, the reaction mixture is heated to the boiling point at which the reaction is completed over a period of 8 hours with the gradual addition of 3 portions of tert-butyl perbenzoate in a total amount of 0.4% by weight. to the amount of monomers.

The prepared acrylic binder has a viscosity of 5 to 10 Pa.s at 25 ° C, a non-volatile content of 48 to 53% by weight. The polymer component has a glass transition temperature of about -8 ° C and a polydispersity of 5.5 to 6.8.

Claims (2)

SUBJECT OF THE INVENTION Solution acrylic binder for ceramic films comprising 40 to 65% by weight of organic solvents, 35 to 60% by weight of acrylic copolymers and optionally up to 10% by weight of plasticizers, characterized in that the acrylic copolymer is a copolymer of polydispersity higher than 4, prepared 2 up to 3 phase free-radical copolymerization of a monomer mixture consisting of 30 to 90% by weight of alkyl esters of acrylic acid having a carbon number of 2 to 8, 10 to 70% by weight of alkyl esters of methacrylic acid having a carbon number of 1 to 8 and optionally up to 8 % by weight of the functional acrylic monomers selected from the group consisting of acrylic and methacrylic acid, their amides / optionally substituted on the nitrogen by methyl, alkyl or alkoxymethyl groups having 1 to 5 carbon atoms and hydroxyalkyl esters having a carbon number in hydroxyal and the glycidyl esters of these acids. 2. A process for the preparation of solution acrylic binders according to claim 1, 2 to 3 by phase radical polymerization of a mixture of monomers in organic solvents in the presence of polymerization initiators, characterized in that the first polymerization phase is conducted at a temperature of at least 53 ° C. up to 40% by weight, and at each subsequent stage, the polymerization temperature and / or solvent content of the reaction mixture is increased such that the last polymerization stage is carried out at a temperature of 70 ° C to the boiling point of the reaction mixture. 65% by weight.