DD140463A1 - PROCESS FOR PRODUCING CROSS-LINKABLE BINDER IN WAESSRED DISPERSIONS - Google Patents

Abstract

The invention relates to a preparation process for crosslinkable binders in aqueous dispersion by way of

Description

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Process for the preparation of crosslinkable binders in aqueous dispersions

The invention relates to a process for the preparation of crosslinkable binders in aqueous dispersion by free-radically initiated copolymerization in an aqueous medium.

The dispersions are suitable for high-quality coating and coating systems on different substrates.

Characteristic of the known technical solutions

It is known j polymers based on acrylic \> zm. Methacrylic acid esters and other ethylenically unsaturated, poly-. merisierbaren produce compounds which th above in'Seitenkefc- given these polymers, functional groups, such as, _e B have Carbo ^ l-, hydroxyl, amide, substituted amide, Acetylaoetonat-, epoxy, etc., and by adding suitable polyfunktioneiler Compounds such as polyvalent epoxies, melamine resins, polyvalent isocyanates undergo crosslinking reactions (Spoor, German Farbzeitohrift 22.7 (1968), S, 307 to 312) o In some cases, such as. If, for example, alkoxyalkylamorylamides or methacrylic amides are used or if the monomers containing epoxy groups and carboxyl groups are used simultaneously, crosslinking is also possible without addition. possible substances (Spoor, German color magazine 22.7 (1968), pp. 307 to 312). The thermal load required for the course of the crosslinking reaction varies widely depending on the reactivity of the components and the frequently used catalysts. Area"

Thus, sometimes a baking at temperatures vjeifc above 100 ⁰ C is required, while on the other hand u. U * can take advantage of catalytic effects even at room temperature or relatively high temperature-sensitive systems, eg hydroxyl-containing polyesters and polyisocyanates, crosslinking reactions * Crosslinkable polymers can be found in solutions, dispersions, solvent-free systems, z. B. corresponding polymers of oligomer character, fusible, reactive powders u * a _c in the textile industry bzi. Paint and coating industry widespread use.

In particular, when using so-called soft or harfcstelle & the monomers, such as higher acrylic acid on the one hand in styrene _s acrylonitrile or methylsethacrylate on the other hand, always critical relationship between elasticity and hardness can be made more favorable by building networked structures »

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Solubility and low quenchability in organic solvents aa also in water is another advantage. Preferred processes for the preparation of such systems are the free-radically initiated emulsion polymerization in aqueous phase and the likewise free-radically initiated polymerization in organic solvents _; often in those with

Water are miscible,

The use of the polymers as coating materials on a wide variety of substrates or as binders for the production of paints takes place predominantly as a result of the dispersion obtained or in the form of the resulting solution. For obvious reasons, the use of aqueous systems with regard to health , Occupational and fire safety and environmental protection easier When coating flexible materials or those that are subjected to bending or breakage, such as ζ "Β. Leather, synthetic substitutes for leather, plastic films; Corresponding metallic substrates also result in particular properties for the properties of the coating system to be used. high requirements * This is the use of crosslinkable polymers in the above. Way described in detail = So, for example, has been proposed for the coating of leather this way. (Süterlin, 5f _e , The Leather 24 (3), 45-54 (1973))

Crosslinking of the polymers used for coating the thermal substrate of the substrate © is problematic, especially when aqueous systems are used for reasons of environmental protection. [0005] It is true that systems are known which allow crosslinking of allow appropriate polymers at sufficiently low temperatures, but their sensitivity to Tvasser severely limits the production in the aqueous phase and the shelf life of such aqueous systems »

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Thus, the preparation and use of isocyanate group-containing polymers which react with substances having reactive hydrogen atoms is known in the literature. Such systems can already react at room temperature or slightly elevated temperature and provide so-called cold-curing or cold-crosslinking coating or bonding agents (DE-OS 1 494 845, DB-OS 1 494 853, DE-OS 2 442 761, DE -IS 1 794 263, H ₈ Spoor, German color magazine 22.7 (1968), pp. 307 to 312).

Naturally, such systems are based on isocyanates for the preparation and application in aqueous phase limits and attempts; In order to avoid the disadvantages of working in organic solvents, to make the Anjajendung in aqueous phase possible via "capped isocyanates" However, the use of higher temperature or longer exposure time is required for a cross-linking * In the already cited work by H. Spoor are given a number of crosslinkable systems, including those that crosslink at sufficiently low temperatures, in order to ensure the application to temperature-sensitive substrates. Mention should be made of methods of preparation for the hydroxyl-containing polymers already mentioned, except for crosslinking with melamine resins in combination with isocyanates, for polymers which are self-crosslinking systems by using N-alkoxy-methylacrylamides as gonomomers for acetylacetate-containing polymers by the use of acetylacetate-containing acrylate ! monomers, crosslinked by formaldehyde or by Autoxydationsprozesse (s. a _e DE-OS 2,236,904 and DS-OS 2,158,957), and for eposyctgruppenhaltiige polymers by use of, for example, glycidyl methacrylate as comonomers _e "The use of epoxide groups in monomers The preparation of crosslinkable polymers in aqueous dispersion is described in US Pat. No. 3,350,339, in which the

Networking by the action of ammonia or amines should be realized »

In contrast, K ₀ Gulbin _$ Das Leder 25, p. 123 (1974) 8US ₃ , states that because of the "sensitivity" of the glycidyl group to water, such polymers could not be applied to the aqueous phase. "

The procedure described in the XJS-PB 3 350 339 does not exclude this possibility and leads to a high degree of crosslinking even during the polymerization *: · Patent DE-OS 2 232 710 claims crosslinkable polymers based on acrolein; which are crosslinked by addition of ammonia or organic amines. The use of (meth) acrylamidomethylenoartylamines (allyl esters) and (M8-oh) -a-allyl amidomethylpyrarboxylic acid allyl esters is described in DS-PS.1 2 08 844 and DE-PS 1 444 068 or DB-OS 2 253 067. Sin Further preparation process for the crosslinkable polymers in aqueous dispersion is the content of the patent DE-OS 2 223 630, in which the use of © C-Halogen ™ alkancarbonsäurevinylester claimed -will. The literature data representing the state of the art of producing crosslinkable polymers in aqueous dispersion has in common that the amount of initiator used ranges from 0.01 "to about 3% by weight, preferably 0, 1 to 3 G0s _e -%, lied on the monomers used.

This will be at one of the principles of the radical. In comparison with solution polymerization, the polymerization process in aqueous emulsion which is initiated is relatively high, but only average to low average molecular weights are achieved for this process.

An extremely low molecular weight is as relevant LösungspolyBier3, s & tßir. Inicht'-required _s because in this respect no Visfcositätsprobleia® aufüre

An extremely high molecular weight is not sought since it is generally accepted by the experts that a high molecular weight favorable for the mechanical properties of a coating is extremely adjusted by the crosslinking process carried out after the application.

The object of the invention is to improve binder dispersions for paint and coating systems so that they can be crosslinked under mild conditions and processed for reasons of labor, health and environmental protection without organic solvents after the preparation "The paint films t> .zw "The coatings which are produced on corresponding substrates after the application of the aqueous binder dispersion should * have an improved weathering resistance, in particular resistance to the effects of water, at the same time high mechanical stress, such as bending, ... buckling strain and impact stress.

Explanation of the nature of the invention

- Problem of the invention

The invention has for its object to develop a process for the preparation of polymeric binders which crosslink under mild conditions for paint and coating systems by free-radically initiated emulsion polymerization in the aqueous phase in the feed process using technically available monomers and excipients to enforced copolymers Crosslinking with high elastic properties with good hardness, good weathering, especially water resistance.

Features of the invention. ...

The object is achieved according to the invention that in a known manner -

A) 35 to 96 parts by weight of esters of ethylenically unsaturated mono- or dicarboxylic acids from an alcohol having up to 12 carbon atoms "preferably esters of acrylic acid with alcohols of the P chain length C ₁ to C _g

B) 5 to 60 parts by weight of vinyl inonomers, such as styrene, oi methylstyrene _s vinyl chloride. Vinylidene chloride and vinyl esters of saturated carboxylic acids.

C) 1 to 15% by weight of ethylenically unsaturated, polymerizable monomethyl or dicarboxylic acids, of acrylic acid, of methacrylic acid, of maleic acid or of monoesters of maleic acid, and

D) 0 to 3 to 15 parts by weight, preferably 1 to 5 parts by weight of epoxide-containing, ethylenically unsaturated; "polymerizable" compounds, preferably glycidyl acrylate or glycidyl methacrylate or in place of D).

E) 0.5 to 15 parts by weight, preferably 1 to 5 parts by weight of hydroxyl-containing, ethylenically unsaturated, polymerisable compounds, preferably. Hydroxyethyl acrylate or "hydroxy " ethyl methacrylate. ·. ,

or 8Ji place of D) or S):

F) 0.5 x bis.15 parts by weight, preferably 1 to 5 parts by weight of derivatives of acrylic or methacrylamide, such as N-hydroxymethylacrylamide, H-But oxyraa thylacr.ylamj.d or * entspre sponding Met'hacrylainidderivate in the aqueous phase according to the known principles of emulsion polymerization by a feed process are polymerized together so that the _T submitted aqueous phase 0 to Oy0075 wt .- #, Toraugsweise 0.001 to 0.0050 wt .- ^ initiator, based on the Monomemischang zn the beginning of the polymerization and O5O5 to 2 parts by weight of initiator, preferably 0.01 to 0.1% by weight of initiator, likewise based on the monomer mixture, are added to the monomer feed and adjusted to the particular monomer used.

Initiatorinenge set a Sensidmenge of 0.7 to 0.01 Gksw "~ $, preferably 0.5 to 0.025 wt -.% In the aqueous template. Use finds «,

In the case of using the eposydgruppenhaltigen monomers listed under D) according to the invention this happens} that at a pH of 2.50 to 4.00 _} preferably from 2.70 to 3j75 and at a moderate 'temperature of 60 to 80 ⁰ G. , Voraugsweise 70 to 75 ⁰ C, is polymerized. The crosslinking required after the application is carried out in a known manner by increasing the temperature and catalyzed by alkalis.

If the bydroxylgruppenhaltigen monomers mentioned under B) are used, it is necessary in carrying out the polymerization, the absence of such a precautionary measure to avoid a high degree of crosslinking during the polymerization process au and it can be moved with respect to temperature and adjusting the pH in the usual way ₀ Crosslinking by The application is done in a known manner with melamine resins or urea-formaldehyde resins.

However, the use of acrylamide derivatives of the type described under F) is, as has often been mentioned in the literature, again to be carried out under special conditions in order to achieve the crosslinking reaction between the methylol and etherified methylol groups, which proceeds at higher temperatures and lower pH values avoid",

According to the invention, in addition to the incorporation of said reactive monomers, the initiator or the initiator system having a concentration of from 0 to 0.100% by weight, preferably 0, is required for achieving the performance effect of high resistance to mechanical stress as shown in the examples _'t 005 to 0.010 wt.% ~ in the vorgelegten'Wäßrigen phase and with 0.005

"bis..2,000-Gew- $, preferably O ₅ OlO" to 0.100 Gew ~ ira to use inflow of the polymerization approach "Of course, depends; the initiator concentration to be used within this range, inter alia, on the nature of the monomers used, their degree of purity and stabilization and the. Purity of the excipients used from, the extremely low initiator content required for setting the desired performance effect, due to a low turnover rate, especially in the execution of the polymerization process in large boiler units thereby. Difficulties lead that either very long and thus economically unfavorable polymerization times are needed, or that at faster feed of the monomer mixture an accumulation of unreacted monomers in. Polymerization reactor takes place, which can lead to quality problems or »dangerously" in sudden polymerization to a very high temperature rise. According to the invention, this risk can be counteracted by adjusting the concentration of the emulsifier used in the original to a specific value determined by the stated limits. It is the rule that with decreasing initiator concentration an increase in the emulsifier content in the template is required *

It is mentioned in the publications of the prior art (EiGuIbin, Das Leder 25, p.123 (1974)) that polymers obtained by copolymerization with glycidyl-containing, polymerizable compounds with suitable substances, such as polyamines or polybasic organic acids at low (crosslinking temperatures * However, because of the sensitivity to compounds with active hydrogen, such copolymers containing glycidyl groups should be applicable only to inert solvents, which is surprising

it is possible by the inventive method to avoid extensive crosslinking during the polymerization process for the preparation of the copolymer and during a reasonable storage time. For a person skilled in the art it is furthermore surprising that such an extremely low amount of initiator is required for the particular application-technological effect. ,

As you know, u, a. the initiator concentration used in the polymerization is the average molecular weight of the resulting polymer. It is also known that polymers with a high average molecular weight generally have better mechanical properties than those which have only limited molecular chains »

However, it is not customary to proceed with crosslinkable, film-forming polymers in this way, since the cross-linking process carried out after the application produces an infinitely large molecular bond, which in turn ensures the setting of high-quality mechanical properties (H. Spoor, Deutsche Farbenzeitschrift 22.7 (German Pat. 1968) S.307). Often, this possibility is even exploited to achieve considerable performance advantages. Thus, the production of binders for paints and .Anstrichstoffe in organic solvents under adjustment of the lowest possible molecular weight, in recent developments with very high! Plants concentrations (high solids, H.Sander u. R. Kroker, paint and varnish, 82, 12, 1976, S, 1105-1111) even in an extreme way. The excellent mechanical properties of the paint and paint films are obtained after the crosslinking process. The low solution viscosity at high solids content associated with the low average molecular weight adjustment ensures a

simple processing of paints "Of course, in the processing of a polymer dispersion a high average molecular weight does not have the same unfavorable effect as polymer solutions, since in this case the molecular weight has no influence on the viscosity of the dispersion." Adjustment of arbitrarily high molecular sizes in the preparation of polymer dispersions not one, so that the manufacturing method according to the invention in the practical realization no disadvantages arise *

Neither this fundamental recognition of the need to set extremely high molecular weights prior to the crosslinking process in order to achieve the desired optimal application engineering effect; nor the resulting special leadership of the polymerization process are mentioned in the literature representing the state of the art. The initiator concentrations used are substantially, and are usually even one order of magnitude higher than suggested by the solution according to the invention. It is also surprising to find the solution which results from the application of such an extremely low initiator concentration with respect to the rate of addition by deliberately adjusting the emulsifier concentration in the original eliminated "»

AIb initiators for the polymerization are zmsskmäßig water-soluble'Perosyde as Kaliimvperoxydisulfat or Ammoniuiaperojqyäisülfat also used an initiation by an E ed ox Sy st era is optionally applicable * It can be mentioned peroxides in combination with reducing agents such as Alkalisal.se the thischweflägen acid, Rongalit

- 1? -

or other substances which are customary for these purposes. "Yields which are likewise customary are predominantly alkyl sulfates or alkyl sulfonates of the chain length C-, ρ-C 1 -, as emulsifier use. To increase the stability of the dispersion to mechanical and chemical influences, it is expedient to use mixtures of these emulsifiers with nonionic surfactants of the alkylene oxide adduct type on alkylphenols, fatty alcohols or fatty acids

! Ausfuhrungsbe games;

The invention will be explained in more detail with reference to the examples below.

Example 1 .

In a provided with the usual technical equipment polymerization reactor is an aqueous phase (template) consisting of

300 parts by weight of "distilled" or "deionized" water 2.5 parts by weight of sodium lauryl sulfate

"prepares the air atmosphere displaced by an inert gas and heated to the polymerization temperature of 70 ⁰ C. After reaching this temperature 0.005 Ge · /.- TIe potassium peroxydisulfate are added and a prepared, well-mixed pre-emulsion consisting of 200 parts by weight TIn water j 5 wt. T In I r at iumlaury la Ulf at O ₅ O3 by weight Tln Ealiumperoxydisulfat 350 parts by weight butyl acrylate 70 parts by weight Tln Tln methyl methacrylate 40 wt. "Tin acrylic acid 40 parts by weight of glycidyl methacrylate Tln

in the course of 3 hours, the polymerisation reactor is fed with a stable dispersion having a pH value of 2.7 and a solid of 50 $, after a postpolymerization time of one hour. The copolymer has a Fiicentscher type in O ₅ 5 25% of 105% cyclohexanone solution at 25 ° C.

After adjusting with aqueous, concentrated ammonia to a pH of 8 and admixing in the leather industry commonly used pigment paste * !, conventional auxiliaries such as, 33. Matting agents and anti-adhesives give a high

high quality coating system for leather finishing. The leathers treated with this are characterized by their high mechanical strength * In detail, the usual test leads to the following results:

Flexing behavior, (measured with the Ballyflexometer)

In dry condition after 100 000 kinks

- perfect material surface

In the moistened state after 50 000 buckling

- perfect material surface

Edge band test at 12O ⁰ G: Perfect material surface

Adhesive strength in dry and moist condition

- grade: good

Rubbing fastness in dry, wet and moisturized condition

- grade: good

Be is pie 3. 2

The procedure is as in Example 1, but the Monomerenmschung consists of

200 parts by weight of TIn acrylic acid butyiester

250 G-ew.-Tln methyl methacrylate 50 G-ew.-Tln 2 - hydroxyethyl acrylate

This gives a stable dispersion with a pesticide of 50 fo · Sach adjusting with aqueous ammonia to a pH value of 8 and addition of 10-15 G-8vV .- $ melamine resin eg Hexakismethoxymethy! Melamine can in the usual way with organic or Inorganic pigments, a paint can be obtained, which is applied to galvanized steel sheet, at drying temperatures between 50 to 120 C _5, preferably 70 to 9O ⁰ C, coatings with high mechanical Beschiebbke it yields «Under certain circumstances, the crosslinking process in a known manner with inorganic or organic acids catalyzed become. Characteristic of the properties of the coating is the high resistance to bending and kinking stress at high hardness,

Example 3

The procedure corresponds to Example ^, the template in the polymerization reactor but 1.0 part by weight of potassium persulfate is added. The testing as a binder for the leather finishing leads to the following result:

Constant bending behavior (Ballyflexoraeter)

In dry condition after 100 000 kinks

- Formation of fine cracks

In the moistened state after 50 000 buckling. ~ Formation of fine pass

Edge band test at 12O ⁰ C

partial damage of the material surface

Adhesive strength in dry and moistened condition «Note; moderate

Rubbing fastness in dry, wet and moisturized condition

- Notes moderately

Example 4

• *

The procedure of Example 1 is used, but in the original of the polyraerization reactor only Ο, 250 parts by weight of sodium sulfate sulfate are used. "The result is a clear, temporary enrichment of the monomer mixture in the reactor, combined with a very un 'regular course of polymerization, marked by violent heat *.

Claims (2)

Process for the preparation of crosslinkable binders in aqueous dispersion for coating and coating systems by emulsion polymerization in the presence of ionogenic and / or non-ionogenic emulsifiers in the feed process, characterized in that in a manner known per se A) 35 to 96 parts by weight of esters of ethylenically unsaturated mono- or dicarboxylic acids from an alcohol having up to 12 carbon atoms, preferably esters of acrylic acid with alcohols of chain length C to Cg B) 5 to 60 parts by weight of vinyl monomers, such as styrene, o ^ -methylstyrene, vinyl chloride, vinylidene chloride and vinyl esters of saturated carboxylic acids C) 1 to 15 parts by weight of ethylenically unsaturated, polymerizable mono- or dicarboxylic acids, such as acrylic acid, methacrylic acid, Maleic acid or half ester of maleic acid and D) 0.3 to 15 parts by weight, preferably 1 to 5 parts by weight of epoxy group-containing, ethylenically unsaturated, polymerisable compounds, preferably glycidyl acrylate or glycidyl methacrylate, or instead of D) E) 0.5 to 15 parts by weight, preferably 1 to 5 parts by weight of hydroxyl-containing, ethylenically unsaturated, polymerisable compounds, preferably c6-hydroxyethyl acrylate or OC hydroxyethyl methacrylate
·. or instead of D) or E) ! 0.5 to 15 parts by weight of preferably 1 to 5 parts by weight of derivatives of acrylic or methacrylamide, such as U-eyeroxy-methylacrylamide, 3-methyl-toxylamide or corresponding methacrylamic derivatives are polymerized with one another in such a way that το the submitted 'aqueous phase O to 0.0075, preferably O ₅ Oolo to O _f OO5O wt .- $ of initiator, based on dieMonomerenmischung beginning of the polymerization and 0.005 "to 2 wt .- $, preferably 0 _f 01 to 0.1 wt .- ^ initiator, also based on the renciischimg Monome, 'the Moiioraerenzulauf added v? ground and a initiator concentration employed depending on Ö3r in the aqueous phase provided an emulsifier \ ^r on 0.7 to ₅ percent by O Ol .-- / Preferably 0.3 to 0.025% by weight is likewise used in the aqueous phase presented. 2 * Process for the preparation of crosslinkable binders according to item I _5, characterized in that in the Palle of the use of the glycidyl-containing, polymerizable compounds designated under D), the pH value during the polymerization process to 2 ^ 70 to 3.75 » the temperature is adjusted to 60 to SO ⁰ C, preferably 70 to 75 ° C, u