EP0084809A2 - Dispersion of acryl plastics - Google Patents

Abstract

New formaldehyde- and acrylonitrile-free acrylic plastic dispersions suitable for the consolidation of fiber structures contain a copolymerized dispersion of 70 to 96.95% by weight alkyl esters of acrylic and / or methacrylic acid or their mixture with styrene, 2 to 30% by weight dispersed in the aqueous phase. % of a hydroxyalkyl ester of an unsaturated carboxylic acid, 1 to 10% by weight of acrylic or methacrylamide, 0.05-3% by weight of comonomers with at least two polymerizable double bonds and optionally up to 5% by weight of unsaturated carboxylic acids and up to 20% by weight .-% other monomers. Fiber structures solidified with the dispersions are distinguished by reduced binder loss during chemical cleaning and by reduced plasticizer absorption.

Description

Field of the Invention

The invention relates to aqueous plastic dispersions which contain no formaldehyde and no acrylonitrile and do not release these substances when the dispersion or the plastic is heated. The invention further relates to its application for solidifying textile fabrics. For this purpose, acrylic plastic dispersions are used which contain N-methylolamide groups or formaldehyde condensation resins as crosslinking agents and / or whose plastic content can be partially made up of acrylonitrile. These dispersions or the plastics contained therein release - at least when heated - small amounts of formaldehyde or acrylonitrile, which is particularly undesirable if products equipped with them are to be used in the food or clothing sector. The content of acrylonitrile or formaldehyde-releasing substances has hitherto been considered indispensable in order to give the products equipped with the dispersions sufficient resistance to chemical cleaning agents.

There is therefore a need for aqueous plastic dispersions which are free of formaldehyde, formaldehyde-releasing substances and Acrylonitrile are and still allow the production of cleaning-resistant solidified fiber structures.

State of the art

A formaldehyde- and acrylonitrile-free acrylate dispersion is known from EP-A 12032, which is suitable for solidifying predominantly hydrophilic fiber structures. The plastic part of the dispersion is largely made up of plasticizing monomers, such as higher acrylic or methacrylic acid esters, and the rest of it made up of plasticizing monomers, such as styrene or methyl methacrylate, and from an unsaturated carboxylic acid. Such dispersions have been known for a long time. Textile fabrics equipped with this have the disadvantage that they are not very resistant to the solvents commonly used in chemical cleaning. Acrylic or methacrylamide or hydroxyalkyl esters of acrylic or methacrylic acid or mixtures thereof can also be used as further comonomers to build up the dispersed plastic. This does not lead to a decisive improvement in the resistance to organic solvents. The fiber structures solidified with these binders can therefore not be used for purposes in which they come into contact with organic solvents, plasticizers or plastic articles produced therewith. Similar binders are proposed in EP-A 12033 for hydrophobic fiber structures; they have the same disadvantages.

Task and solution

Acrylonitrile and formaldehyde-free acrylic plastic dispersions suitable for solidifying fiber structures should be improved to the extent that the fiber structures solidified therewith have sufficient resistance to the solvents used in chemical cleaning and to plasticizers. The properties of such fiber structures which have been produced using conventional, self-crosslinking acrylic resin dispersions can be used as a yardstick for sufficient resistance. These dispersions always contain N-methylolamide groups, from which small amounts of formaldehyde can be split off, and in some cases acrylonitrile. The task is accomplished by acrylic plastic dispersions with the composition of the plastic specified in the main claim.

Advantage of the invention

The following table compares the evaluation results that were obtained on textile fabrics that had been solidified with various binders under standardized test conditions. One test consists in determining the loss of binders during chemical cleaning with trichlorethylene at 20 ° C. In the other test, the swelling is determined after storage for 4 hours in methyl isobutyl ketone at room temperature. This test leaves sensitivity to plasticizers detect. In both cases, low numerical values are aimed for.

A conventional self-crosslinking acrylic dispersion and various other acrylic dispersions were used as binders, which are free of acrylonitrile and formaldehyde-releasing substances and which were made from a mixture of higher acrylic and methacrylic esters as well as a hydroxyalkyl ester, an unsaturated carboxylic acid and optionally with acrylamide. It has been shown that the sensitivity of the solidified fiber structures to organic cleaning agents and plasticizers is considerably greater than when using known self-crosslinking acrylic dispersions and leads to results which are practically unusable.

Test specimens are an impregnated and dried at 80 ° C polyester fabric with a binder layer of 50 wt .-% in the determination of the binder loss and in the determination of the methyl isobutyl ketone absorption polymer films of 30 x 30 mm in size and 0.5 mm in thickness, which by drying the dispersion at 35 ° C.

^* ) and condensing at 140 ° C for 5 min

Surprisingly, the resistance to organic cleaning agents and plasticizers is significantly increased if small amounts of a multifunctional crosslinking agent are involved in the build-up of the binder. In principle, it is of course known that the resistance of a binder to organic solvents and plasticizers can be improved by crosslinking. However, since crosslinking affects film formation, it has previously been considered essential to bring about crosslinking, for example by means of N-methylolamide groups, only after film formation when heated. The plastics according to the invention are therefore only crosslinked to such a small extent that perfect film formation is possible. It was not to be expected that such a low level of crosslinking could have a lasting effect on the resistance to organic solvents and plasticizers. In fact, the increased resistance is not based solely on the crosslinking, but rather on a synergistic interaction of the crosslinking agent with the amide groups and hydroxyalkyl ester groups. It is not known how this synergism comes about, but it turns out that each of the three components mentioned is indispensable for the high durability achieved.

Industrial applicability

Thanks to the increased resistance of the films produced from the dispersions according to the invention to organic solvents and plasticizers, the new dispersions can be used successfully wherever previously self-crosslinking acrylic plastic dispersions were used with N-methylolamide groups. The consolidation of textile fabrics is a preferred area of application.

Preparation of the dispersions according to the invention

The predominant structural component a) consists of the acrylic or methacrylic esters characterized in the main claim, some, but generally not more than half, of which can be replaced by styrene. Among the acrylic and methacrylic acid alkyl esters, those with at least 4 carbon atoms in the alkyl radical are particularly preferred, in particular n-butyl acrylate and methacrylate and 2-ethylhexyl acrylate. High proportions of these esters ensure a low minimum film formation temperature (according to DIN 53787) and a low dynamic freezing temperature (according to DIN 53445). The minimum film formation temperature of the dispersion is preferably below 70 ° C. and the dynamic freezing temperature of the films produced therefrom is preferably below 40 ° C. These values are essentially determined by the choice of the ester component a). As is known, styrene and the lower alkyl esters of methacrylic acid have an increasing effect on these values, while they are reduced by acrylic acid esters and higher methacrylic acid esters.

Esters of acrylic acid, methacrylic acid, maleic acid, fumaric acid or itaconic acid can be used as the hydroxyalkyl ester component b). They contain at least 2 and generally not more than 12, preferably at most 4 carbon atoms in the hydroxyalkyl radical. Preferred monomers of this type are hydroxyethyl acrylate and methacrylate, 2-hydroxypropyl acrylate and methacrylate and 4-hydroxybutyl acrylate and methacrylate. The preferred proportion of component b) in the copolymer is 3 to 15% by weight.

Acrylic and / or methacrylamide are used in an amount of 1 to 10, preferably 2 to 6% by weight.

Crosslinking comonomers d) with at least two polymerizable carbon double bonds can be compounds which contain double bonds of the same or different reactivity. Examples of the former are acrylic and methacrylic esters of glycols, such as ethylene glycol, diethylene glycol, 1,4-butanediol; Methylene bis-acrylamide and methacrylamide, divinylbenzene, diallyl phthalate and triallyl cyanurate. Crosslinking monomers with different reactivity of the double bonds are, for example, vinyl methacrylate, allyl acrylate and allyl methacrylate. The amount of the crosslinking comonomer depends on its crosslinking activity, which depends on the reactivity of the double bonds and on the molecular weight of the monomer. With proportions below 0.05% by weight, calculated on the weight of the copolymer, the desired improvement in solvent resistance is generally not achieved to a sufficient extent. If the proportion exceeds 3% by weight, film formation can be disturbed. Within the range of 0.5 to 3% by weight, the solvent resistance of the films increases with increasing crosslinking and is appropriately chosen so high that the film formation is just not affected. The preferred level of crosslinking monomers is 0.1 to 1% by weight.

Unsaturated carboxylic acids do not necessarily have to be involved in the structure of the copolymer, but a proportion of up to 5% by weight, based on the weight of the copolymer, can improve the stability of the dispersion. Fractions of 0.5 to 3% by weight are usually sufficient for this. Acrylic or methacrylic acid is preferably used. Other usable unsaturated polymerizable mono- or dicarboxylic acids are crotonic acid, maleic acid, fumaric acid and itaconic acid.

In limited amounts, which do not exceed 20% by weight, other monomers can be involved in the construction of the copolymer, provided that it is not acrylonitrile or methacrylonitrile and does not contain any formaldehyde-releasing groups. These are to be understood as groups which, at least when heated, can lead to the release of formaldehyde. These include, above all, N-methylol amide groups, and also blocked methylol groups, such as Man _h i _b h bases or N-amide methylol alkyl ethers. Additional monomer components f) are generally not required for the purposes of the invention, but can be expedient if certain tasks are thereby performed. An example is the incorporation of N-vinylimidazole or of dialkylaminoalkyl esters of acrylic or methacrylic acid or of their salts. In a proportion of, for example, 1-5% by weight, these comonomers improve the affinity of the plastic for cellulose fibers. Examples of further comonomers which can be used for other purposes are N-vinylpyrrolidone, vinyl acetate and other vinyl esters, vinyl chloride, vinylidene chloride, butadiene, ethylene and propylene.

The dispersions according to the invention can be produced by the known processes of emulsion polymerization in the presence of the anionic, nonionic or cationic emulsifiers and water-soluble free-radical initiators commonly used. Anionic emulsifiers or combinations of anionic and nonionic emulsifiers are preferably used. The average particle diameter (weight average) can be between 20 and 2000 nm and is preferably 100 to 500 nm. The solids content is preferably between 50 and 70% of the total weight.

application

The preferred field of application for the dispersions according to the invention is the solidification of textile fabrics. These include nonwovens, wadding, fabrics and knitted fabrics made from natural or synthetic fibers or their mixtures. Quantities of, for example, 1 to more than 100% by weight of plastic, based on the weight of the fiber, can be used for consolidation. 10 to 30% by weight are preferably used for nonwoven bonding. The method of introduction depends in a known manner on the nature of the fiber structure and the amount of dispersion to be applied.

The usual application methods, such as spraying, impregnation, splashing, knife coating, can be used in a known manner. The treated fiber material should be dried at temperatures above 100 ° C., preferably in the range from 120 to 160 ° C.

Other flat substrates, such as paper, wood, plastic films, sheets, etc. can be coated with the dispersions according to the invention, optionally after pigmentation, and are then likewise dried at temperatures above 100 ° C. The film solidifies during drying and maintains its high resistance to organic solvents and organic plasticizers.

Examples

Production process of the dispersions according to Examples 1 to 6.

• 240 Teilen vollentsalztem Wasser 1 Teil 90 %iger sulfonierter äthoxylierter Alkyl-arylol-maleinsäure 0,9 Teilen Ammoniumperoxodisulfat 395 Teilen der Monomerenmischung gemäß nachfolgender Tabelle

In a 1 liter round-bottom flask equipped with a stirrer and contact thermometer, 155 parts of demineralized water were heated to 80 ° C. with stirring and dissolved in 5 parts of butyl methacrylate with 0.16 part of a 90% sulfonated ethoxylated alkyl-arylol-maleic acid. and mixed with 5 parts of a 4% ammonium peroxodisulfate solution. Then, after a pause of 4 minutes at 80 ° C, an emulsion was formed within 4 hours:

• 240 parts of demineralized water 1 part of 90% sulfonated ethoxylated alkyl arylol maleic acid 0.9 part of ammonium peroxodisulfate 395 parts of the monomer mixture according to the table below

dripped. The temperature was then kept at 80 ° C. for a further 2 hours. The mixture was then cooled to room temperature and the pH was adjusted to 2.2 by adding phosphoric acid. Stable, coagulate-free dispersions were obtained.

The following table shows the results of the performance test of the dispersions in the two columns on the right. "BTV" denotes the binder loss (in% by weight, based on binder weight) of a polyester fabric consolidated with 50% by weight (based on fiber weight) of binder Treatment with trichlorethylene in a laboratory washing machine. "MIBK absorption" denotes the swelling after storage for 4 hours in methyl isobutyl ketone at 20 ° C., measured in% by weight, based on the binder weight.

Production process of the dispersions according to Examples 7 to 11.

zugetropft. Anschließend wurde die Temperatur 2 weitere Stunden auf 80°C gehalten. Danach wurde auf Raumtemperatur abgekühlt und der pH-Wert mit Phosphorsäure auf 2,2 eingestellt.In a 1 liter round-bottom flask equipped with a stirrer and contact thermometer, 155 parts of fully demineralized water and 0.06 part of an emulsifier which had been obtained by reacting 1 mol of tributylphenol with 7 mol of ethylene oxide, sulfating and converting to the sodium salt were stirred on Heated 80 ° C and mixed with 5 parts of a 4% ammonium peroxodisulfate solution. Then an emulsion was formed at 80 ° C within 4 hours

dripped. The temperature was then kept at 80 ° C. for a further 2 hours. The mixture was then cooled to room temperature and the pH was adjusted to 2.2 using phosphoric acid.

Stable, coagulate-free dispersions were obtained.

Claims (4)

1. Acrylic plastic dispersion free of formaldehyde, formaldehyde-releasing substances and acrylonitrile, containing a dispersed copolymer in the aqueous phase a) 70-96.95% by weight of alkyl esters of acrylic or / and methacrylic acid having 1 to 18 carbon atoms in the alkyl radical or a mixture thereof with styrene, b) 2-30% by weight of hydroxyalkyl esters of an unsaturated polymerizable mono- or dicarboxylic acid with at least 2 carbon atoms in the hydroxyalkyl radical, c) 1-10% by weight of acrylic or methacrylamide, d) 0.05-3% by weight of crosslinking comonomers with at least two polymerizable double bonds, e) 0 - 5 wt .-% unsaturated polymerizable mono- or dicarboxylic acids and optionally f) 0-20% by weight of further comonomers which contain no nitrile groups and no formaldehyde-releasing groups. 2. Plastic dispersion according to claim 1, characterized by a minimum film formation temperature below 70 ° C. 3. Plastic dispersion according to claim 2, characterized by a dynamic glass transition temperature of the dispersed copolymer under 40 ° C. 4. Use of plastic dispersions according to claims 1 to 3 for solidifying textile fabrics.