CS256493B1 - Solution acrylic binders and process for their preparation - Google Patents

Abstract

The solution relates to solution-based acrylic thermoplastic, thermosetting and chemically curable binders for coatings, printing inks, adhesives, impregnation agents and other applications. The purpose of the solution is improved mechanical properties of the films and their better adhesion to the substrate, high integrity and reduced permeability to gas, water and other aggressive substances and excellent mechanical properties of cured three-dimensional networks. This is achieved by using binders containing organic solvents and acrylic polymers prepared from a mixture of acrylic and/or methacrylic acid esters with aliphatic alcohols with 1 to 12 carbon atoms, optionally unsaturated monomers from the group including styrene, its alkyl derivatives with 1 to 4 carbon atoms in the alkyl chain and vinyl acetate, and acrylic monomers and carboxyl, hydroxyl, amidic and oxirane functional groups, radical polymerization carried out by controlled continuous or gradual addition of a mixture of monomers to solvents or a mixture of solvents at the boiling temperature, further reacting the reaction mixture at the specified temperature for a certain time and optionally distilling off part of the solvents.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to resin-based acrylic thermoplastic, thermosetting and chemically curable binders of pigmented and non-pigmented coatings, printing inks, adhesives, impregnating agents, or other applications characterized by suitable chemical and molecular distribution of macromolecular chains. secured by a controlled preparation process ·

Polymer solutions are prepared either by direct dissolution of homopolymers or copolymers in suitable solvents, or by solution polymerization or copolymerization of various monoethylenically unsaturated monomers in the presence of organic solvents. Since solution polymerization is usually less time-consuming and technologically demanding than the process of preparing a solid polymer and its subsequent dissolution in organic solvents, it is also more frequently used to prepare solution polymers · Successful solution polymerization requires the selection of such a solvent or solvent mixture to achieve molecular dissolution However, the solvent used is not only an inert reaction medium for solution polymerization, but also affects the molecular weight, molecular weight distribution and structure of the polymer molecules, and thus the properties of the end product, in particular through the different degrees of chain transfer.

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Vela! A serious problem for all solution polymerizations is the dissipation of the heat of the process and ensuring the thermal controllability of the process. · For these reasons, the polymerization is carried out either in a large excess of solvents} to dissipate the heat of reaction and cool the reaction mixture mostly by refluxing condensed vapors; or by gradually adding monomers or a mixture of monomers and solvents Usually, in these technologies, maintaining the thermal regime of the reaction is a priority for all other problems. The polymerization process is conducted so as to maintain the boiling of the reaction mixture at the desired reflux so that the addition of monomers slows down or interrupts as needed. or vice versa, accelerating ·

Only the usual quality parameters can be guaranteed for the final product, such as · content of non-volatile components, viscosity, color etc. · but not the regular molecular character of the polymer component · Modern polymer binders, among which solution acrylic binders occupy a particularly important position to meet a number of demanding requirements resulting from progressive ways of their application. For example, for some solution polymers, compatibility with other types of higher molecular weight binders, which is highly dependent on the high molecular weight content of the binder polymer component, is required. Elsewhere, the presence of low molecular weight and oligomeric components that migrate to the substrate, reduce adhesion to the substrate or cause permanent film stickiness and decrease its surface hardness is poor, poor reproducibility of the macrombleicular chain chemical structure causes serious disproportion in application properties of molecularly uncontrolled solution polymerization products.

The present invention is directed to solution acrylic binders. The subject matter of the present invention is that the binders contain 20 to 60% by weight organic solvents and 40 to 80% by weight organic solvents.

256,493 acrylic polymer having a number average molecular weight of 3,000 to 60,000 and a weight to number average molecular weight ratio of 2 to 6 while maintaining random distribution of monomer segments. Acrylic polymer prepared from a mixture of 30 to 100 wt. parts by weight of esters of acrylic and / or methacrylic acid with aliphatic alcohols having 1 to 12 carbon atoms, optionally up to 100 wt. parts by weight of unsaturated monomers from the group comprising styrene, its C1-C4 alkyl derivatives and its vinyl acetate, and up to 40 wt. parts of acrylic monomers having carboxyl, hydroxyl, amide and oxirane functionalities are obtained by controlled free-radical polymerization of the above monoethylenically unsaturated monomers by controlled continuous or sequential addition of a mixture of monomers with an initiator to the present solvent or a mixture of moderate reflux reflux liquids few. The final stage of preparing the acrylic binder may be supplemented by distilling off a portion of the solvents to increase the proportion of non-volatile components in the final product.

The solution acrylic binder prepared according to the invention has a number of advantages over similar binder types. Thus, in particular, by selecting different types and amounts of starting monoethylenically unsaturated monomers, the physico-mechanical properties of the polymer component of the binder in the dried state, optionally after thermal or chemical curing, can be varied to a large extent. Relatively broader polydispersity than corresponds to the batch process for the preparation of similar solution polymers also improves the mechanical properties of the film and guarantees its better adhesion to the substrate. The regular random chemical distribution of the macromolecular chain segments allows maximum intermolecular force application, which ensures high integrity of the coating and reduces gas permeability, void, or ionically dissolved aggressive substances, thus enhancing the protective properties of the coating. of chains between nodes * and thus create preconditions for excellent mechanical properties of cured three-dimensional networks.

In particular, esters of acrylic acid and methacrylic acid with aliphatic alcohols with the exception of tertiary alcohols having 1 to 12 carbon atoms, such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol , n-pentanol, isopentanol, 2-methylbutanol, 2-pentanol, 3-pentanol, n-hexanol, 1-methylpentanol, 3-methylpentanol, 2-ethylbutanol, 2-methylpentanol, n-heptanol,

1-methylhexanol, 2-methylhexanol, 3-methylhexanol, 3-heptanol, 2-ethylpentanol, n-octanol, isooctanol, 2-ethylhexanol, 3,5,5-trimethylhexanol, n-decanol or dodecanol. The acrylic binder of the present invention can also be formed with only one or only a few esters of acrylic and / or methacrylic acid with the above alcohols, without the addition of monomers from the other groups mentioned herein.

The other copolymer component may comprise up to 100 parts by weight of non-acrylic monoethylenically unsaturated monomers selected from vinyl acetate, styrene and its C1-C4 alkyl substituents such as alpha-methylstyrene, beta-methylstyrene, 2- methylstyrene, 3-methylstyrene, 4-methylstyrene and tert-butylstyrene. The addition of styrene or its alkyl derivative increases the surface hardness of the dried film, while vinyl acetate contributes to improving adhesion to the substrate and increases the tackiness of the film surface.

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Furthermore, acrylic monomers with carboxylic, hydroxyl, amide or oxirane functional groups can also be an important component of the copolymer according to the invention. Of the carboxyl group-containing monomers, acrylic acid and methacrylic acid are used in the present invention. Holders of the hydroxyl group are hydroxyalkyl derivatives of acrylic and methacrylic acids having a carbon number in the 2-4 alkyl group, of which 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate are particularly used.

Among the monomers containing amide groups, acrylic amide, methacrylamide, methylolamides of acrylic acid and methacrylic acid, methylolamides of these acids etherified with C1-C4 alcohols such as N-methoxymethylacrylamide, N-methoxymethylmethacrylamide, N-butoxymethacrylamide, n-butoxymethacrylamide N-isobutoxymethylacrylamide, N-isobutoxymethylmethacrylamide, and the like, optionally also n-alkyl substituted acrylic or methacrylic amides having 1 to 5 carbon atoms in the alkyl substituent such as Ν, Ν-dimethylacrylamide, Ν, Ν-dimethylmethacrylamide, N N-tert-butyl methacrylamide, Ν, »-dibutyl acrylamide, N, N d dibutyl methacrylamide and the like, and optionally other acrylic or methacrylic acid amide substitution derivatives, allowing physical or chemical formation of the three-dimensional network. Of the oxirane-containing monomers, glycidyl acrylate and glycidyl methacrylate are recommended. The functional monomers of the present invention can be used either singly or in any combination, up to 28.6% by weight. starting mixtures of monomers.

Organic solvents which comprise 20 to 60 wt. of a solution acrylic binder according to the invention, is

258 493 chooses the binder and its application according to the requirements of the production technology. From a technology point of view, the choice of solvents for solution polymerization should take into account especially the transfer constants, the dissolving capacity and the boiling points. The chain transfer and polymerization temperature determine the molecular weights of the polymer. In order to form a homogeneous, homogeneous solution, the solvent polymer must dissolve well. The nature of the solvents is also governed by the application requirements and the polymer curing process. In the case of curing with polyisocyanates, all solvents with active hydrogen must be excluded. Aromatic hydrocarbons such as toluene, xylene, ethylbenz® and the like can be used, esters such as ethyl acetate, propyl acetate, butyl acetate, isobutyl acetate, glycol ethers such as monoethylene glycol monoethyl ether acetate, glycol diesters such as ethylene glycol diacetate, and the like. e.g. n-propanol, isopropanol, n-butanol, isobutanol and others. In some cases, aliphatic hydrocarbons may also be used, for example in the form of petroleum spirit or white spirit. Polymerization hexane is also suitable. The possibilities of using various organic solvents are not limited by the present invention.

The solution acrylic binders of the present invention are typically prepared in a stirred reactor equipped with a jacket for heating and cooling, a reflux condenser, and a monomer / initiator dosing device. This mixture is prepared in a separate stirred vessel. As polymerization initiators, organic peroxides, hydroperoxides, peracid esters or diazo compounds, such as dibenzoyl peroxide, di-tert-butyl peroxide, tert-butyl hydroperoxide, dicumyl peroxide, cumene hydroperoxide, tert-butyl perbenzoate, azo-bis-isobutyronitrile are used. 0.3 to 5 wt. to monomers.

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The polymerization itself is carried out by adding a mixture of monomers and an initiator, either continuously by means of a metering pump or sequentially, for example by means of a linear dispenser, to the present solvent mixture heated to the boiling point with a slight reflux of condensed vapors. The polymerization temperature is between 55 and 150 ° C. The dosage oak must be adjusted so as to avoid interrupting, slowing or accelerating the addition of the monomer / initiator mixture due to the exothermic reaction. The addition of the monomers usually takes 1 to 6 hours, depending on how reactive the monomers are and the molecular weight of the polymer to be achieved. Upon completion of the monomer feed, the polymerization is completed within 2 to 12 hours with optional addition of initiator up to a maximum of 3% per monomer. In the final stage of preparation, some of the solvents may be distilled off or replaced with other solvents that are more advantageous in application.

Said process for preparing acrylic binders provides a polymer having a polydispersity of 2 to 6, while at the same time achieving random distribution of monomer segments in the copolymer chains. The number average molecular weights of the polymers prepared by the process described are between 3,000 and 60,000.

The solution acrylic binders of the present invention are suitable for the preparation of paints, inks, adhesives, impregnating agents and the like. They are characterized by high durability, chemical resistance and excellent application properties.

The composition of the solution acrylic binders and the process for their preparation are further exemplified. Parts and percentages given herein are by weight.

Example 1 2δβ 493

A mixture of 100 parts of butyl methacrylate and 3 parts of di-tert-butyl peroxide is continuously added over a period of 2 hours to a solvent mixture consisting of 70 parts of white spirit and 30 parts of n-butanol maintained at a boiling point of 116 ° C with moderate reflux. The polymerization is completed at boiling point for a further 12 hours, with additional initiator batches of 0.3% added to the monomers at 2 hour intervals.

The prepared acrylic binder has a viscosity of 200 to 400 mPa · s at 25 ° C, a nonvolatile content of 49 to 51% by weight, a number average molecular weight of 6,000 to 8,000, a polydispersity of about 3.6. It is suitable for the preparation of paints.

Example 2

The monomer mixture, consisting of 79 parts of styrene, 100 parts of butyl acrylate, 16 parts of 2-hydroxyethyl acrylate, 5 parts of acrylic acid, is mixed with 2 parts of di-tert-butylperoxide. Thereafter, 200 parts of a mixture of xylene and n-butanol (2: 1), maintained at a boiling point of 123 ° C with a slight reflux of condensed vapors, are added continuously through the metering pump over a period of 2 hours. In the next stage of binder preparation, the polymerization is completed at boiling point for 6 hours, with additional initiator doses of 0.5% added to the monomers at 2 hour intervals.

The prepared acrylic binder prepared has a viscosity of 600-1000 mPa · s at 25 ° C, a nonvolatile content of 49-51% by weight, a number average molecular weight of about 12,000 at a polydispersity of 2.8 and an even distribution of the starting monomer segments. It is suitable for the preparation of stoving paints in combination with amino resins.

Example, 3

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A monomer mixture consisting of 54 parts of butyl acrylate, parts of methyl methacrylate, 11 parts of 2-hydroxypropyl methacrylate, 5 parts of methyl acrylamide and 4 parts of acrylic acid is mixed with 3 parts of cumene hydroperoxide. It is then added sequentially with a linear feeder so that the intervals between the individual doses are equal to the duration of the monomer / initiator mixture. The total loading time of the monomer / initiator mixture is 4 hours. The present solvent is 30% monoethylene glycol monobutyl ether acetate per monomer mixture maintained at 140-145 ° C.

After all the monomers have been introduced, the polymerization is completed at the indicated temperature for a further 4 hours.

The prepared acrylic binder has a viscosity of 1,800 to 2,400 mPa · s at 25 ° C, a non-volatile content of 72 to 76% by weight, a number average molecular weight of 4,000 to 7,000, a polydispersity of 3.3 with a random chemical molecule distribution. water.

Example 4

A monomer mixture consisting of 100 parts of butyl acrylate, parts of styrene, 28 parts of N-isobutoxymethyl acrylamide and 5 parts of acrylic acid is mixed with 3 parts of di-tert-butyl peroxide. It is then continuously added over a period of 4 hours to a mixture of xylene and n-butanol (1: 1) which is fed to the reactor in an amount corresponding to the weighed monomer / initiator mixture. The polymerization is carried out at the boiling point of the present solvent mixture at a slight reflux of condensed vapors. After the entire amount of the monomer / initiator mixture has been introduced, the polymerization is completed at boiling point for a further 7 hours, adding a further 3 portions of initiator in an amount of 0.5% per monomer at intervals of 1 h, 3 h and 5 h. mixtures of monomers.

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The prepared acrylic binder prepared has a viscosity of 1.0 to 2.0 Pa.s at 25 ° C, a non-volatile content of 47 to 50% by weight, an acid number of 18 to 26 mg KOH / g polymer, a number average molecular weight of about 22,000, of polydispersity 5.1 at random distribution of functional segments in the polymer chain. It is suitable for transporting self-curable coatings at temperatures of 170 to 180 ° C or firing in combination with amino resins or epoxy resins. It is characterized by high resistance to chemicals.

Example 5

The monomer mixture, consisting of 35 parts methyl methacrylate, 45 parts butyl acrylate, 18 parts styrene and 2 parts acrylic acid, was mixed with di-tert-butyl peroxide added in an amount of 0.8% per monomers. Then, 70 parts of this mixture is slowly added over 4 hours to 30 parts of butyl acetate at a boiling point of 126 ° C with a slight reflux of condensed vapors. The polymerization is then continued for a further 8 hours with an addition of 0.3% initiator to monomers at intervals of 4 h and 6 h after the dosing of the monomer / initiator mixture is complete.

The prepared acrylic binder has a dry matter content of 68 to 72% by weight. Dilute with xylene or butyl acetate to a viscosity of 3.8 to 4.5 Pa.s at 25 ° C and a dry matter content of 50 ± 2% by weight. The number average molecular weight is 28,000 to 36,000 at a polydispersity of 2.9 and a random distribution of monomer segments. It is suitable for preparation of coatings with high resistance to weathering.

example 6 ^{256 493}

A monomer mixture consisting of 70 parts of 2-ethylhexyl acrylate, 27 parts of butyl methacrylate, 3 parts of glycidyl methacrylate and 7 parts of methacrylic acid is mixed with dibenzoyl peroxide in an amount of 0.7% per monomers. Then 40 parts of this mixture are added continuously over 4 hours to 60 parts of a 1: 1 mixture of ethyl acetate and isopropanol, maintained at a boiling point of 78 ° C by a slight reflux of condensed vapors.

After all the monomers have been introduced, the polymerization is continued at the boiling point for a further 10 hours, with an additional initiator of 0.3% added to the monomers at 2-hour intervals. Finally, 25% of the solvents are distilled off and replaced with n-hexane or petroleum ether.

The prepared acrylic binder prepared has a viscosity of 30 + 5 Pa.s at 25 ° C, a non-volatile content of 39 to 42%, a number average molecular weight of 30,000 to 55,000 at a polydispersity of 2.2 and a random distribution of monomer segments. It is suitable for preparing adhesives.

Example 7

A monomer mixture consisting of 80 parts of 2-ethylhexyl acrylate, 20 parts of methyl methacrylate, 40 parts of vinyl acetate, 7 parts of acrylic acid and 3 parts of N, N-iibutyl acrylamide is mixed with 2,2 ' -azo-bis-isobutyronitrile in an amount of 0. 5% to monomers. Then 60 parts of this mixture are added continuously over 3 hours to 40 parts of acetone at a boiling point of 56 ° C. The polymerization is then continued at boiling point, with additional initiator portions of 0.1% per monomer added at 2 hour intervals. After 10 h from the end of the monomer / initiator feed, 1/4 of the acetone was distilled off and 50 parts of ethyl acetate / toluene (1: 1) were added. The polymerization is then completed at a boiling point of 84 ° C for a further 6 hours.

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The prepared acrylic binder prepared has a viscosity of 4 to 7 Pa.s at 25 ° C, a dry matter content of 30 to 32% by weight, a number average molecular weight greater than 40,000, a polydispersity of 4.2. It is suitable for preparing adhesives.

Example 8

A monomer mixture consisting of 50 parts of butyl acrylate, parts of vinyltoluene, 9 parts of 2-hydroxymethyl methacrylate and 3 parts of methacrylic acid is mixed with tert-butylperoxide in an amount of 1.2% per monomers. amount of xylene maintained at a boiling point of 136 ° C with moderate reflux of condensed vapors · Polymerization is completed in another 9 h, adding 2 additional 0.3% initiator batches to the monomers 3 h and 6 h after the end of dosing. monomer mixtures ·

The prepared acrylic binder prepared has a viscosity of 200 to 500 mFa.s at 25 ° C, a nonvolatile content of about 50% by weight, a number average molecular weight of 6,000 to 12,000 at a polydispersity of 3.7, and a random distribution of monomer segments. It is suitable for preparing polyisocyanates at normal temperature.

Claims (2)

SUBJECT OF THE INVENTION 256 493 Solution acrylic binders, characterized in that they contain 20 to 60 wt. % organic solvents and 40 to 80 wt. an acrylic polymer having a number average molecular weight of 3,000 to 60,000 and a weight to number average molecular weight ratio of 2 to 6 while maintaining random distribution of monomer segments prepared by free-radical polymerization of 30 to 100 wt. parts of alkyl esters of acrylic and / or methacrylic acid having a number of carbon atoms in the alkyl group of 1 to 12, optionally up to 100 wt. parts by weight of unsaturated monomers selected from the group consisting of styrene, its alkyl derivatives having a carbon atom number of 1 to 4 and vinyl acetate, and up to 40 wt. parts of functional acrylic monomers selected from the group consisting of acrylic acid and meftiacrylic acid, their amides optionally substituted on the nitrogen by methyl or alkyl or alkoxymethyl groups having a carbon number of 1 to 5, hydroxyalkyl and methacrylic acid derivatives having a carbon number of 2 to 4 , glycidyl acrylate and glycidyl methacrylate. 2. A process for the preparation of polymeric acrylic binders as claimed in claim 1, characterized in that the mixture of monomers with a polymerization initiator is added in a time-controlled continuous or sequential manner to the solvents at their boiling point for a period of 1 to 6 hours. after a period of 2 to 12 hours, eventually some of the solvents are distilled off.