WO1995015994A1 - Plastisol composition - Google Patents

Abstract

The description relates to a plastisol composition based on pearl polymers. The pearl polymers preferably have a core/shell structure and an average diameter of 1 to 150 νm. They are advantageously free of chlorine and consist at least of a) styrene, α-methyl styrene and/or p-methyl styrene and b) 2 to 20 wt. % (in relation to the copolymer) of olefinically unsaturated carboxylic acids. The plastisol composition of the invention can be used in the production of coating compounds, sealants and adhesives.

Description

 'Plastisoi composition'

The invention relates to a novel plastiso composition based on bead polymers, plasticizers and inorganic fillers and, if appropriate, other conventional additives.

Plastisols are generally understood to mean dispersions of organic plastics in plasticizers which gel when heated to a higher temperature and harden when cooled. The plastisols which are still used in practice today contain predominantly fine-powdered polyvinyl chloride (PVC) which is dispersed in a liquid plasticizer and forms a paste. Such polyvinyl chloride plastisols are used for a wide variety of purposes. Among other things, you will as sealing compounds, e.g. used for seam seals in metal containers or as flanged seam adhesives in the metal industry, as corrosion protection coatings for metals (for example as underbody protection for motor vehicles), for impregnating and coating substrates made of textile materials (e.g. as carpet backing), as cable insulation etc. .

However, a number of problems arise in the manufacture and use of PVC plastisols. Even the production of PVC itself is not without its problems, because the workers in the production facilities are at risk of health from the monomeric vinyl chloride

ERSÄΓZBLÄΓT (RULE 26) are exposed. Residues of monomeric vinyl chloride in PVC could also be hazardous to health during further processing or for end users, although the content is generally only in the ppb range.

It is particularly serious when using PVC plastisols that the PVC is both sensitive to heat and light and tends to split off hydrogen chloride. This is particularly a serious problem when the plastisol has to be heated to a higher temperature, since the hydrogen chloride released under these conditions has a corrosive effect and attacks metallic substrates. This applies in particular if relatively high baking temperatures are used to shorten the gelling time, or if, as with spot welding, locally high temperatures occur.

The biggest problem arises in the disposal of waste containing PVC: in addition to hydrogen chloride, U. Dioxins arise, which are known to be highly toxic. In connection with steel scrap, PVC residues can lead to an increase in the chloride content of the steel melt, which is also disadvantageous.

It is therefore the aim of the invention to develop a polyvinyl chloride-free plastiso composition whose application properties correspond to those of PVC plastisols.

Coating compositions based on polyurethane or acrylate have already become known which, for. B. used in the automotive industry instead of PVC plastisols.

The application of two-component polyurethane systems differs fundamentally from conventional plastisols, and users stand for them

ERSÄTZBLÄΓT (RULE 26) Processing complex equipment usually not available.

One-component polyurethane systems are also known, but they all have a number of other disadvantages:

- Moisture-curing systems have a high viscosity and therefore cannot be applied without solvents.

In systems with blocked isocyanate groups, the volatility of the blocking agent can lead to the formation of bubbles in the case of thick layers; moreover, the applicable temperature range between 150 ° C. and 180 ° C. for the stoving conditions is often not to be kept.

- Because of the water to be evaporated, aqueous PU dispersions do not fit into the usual production process.

- Microencapsulated polyurethane systems lack shear stability, which leads to gelation in the pumps during application.

Acrylate plastisols, as have become known from DE-B-24 54 235 and DE-B-25 29 732, largely meet the technical requirements mentioned at the outset, but the required acrylate polymers are also far more expensive than polyvinyl chloride, so that they are used Such acrylic plastisols have hitherto been limited to special fields of application, for example as spot welding pastes, in which PVC plastisols fail completely. Plastisols based on styrene / acrylonitrile copolymers according to EP-A-261 499 are also not yet a satisfactory solution because of inadequate abrasion resistance and / or storage stability.

DE-A-41 39382 proposes plastisols based on core / shell polymers, in which the core of the polymer particles is formed from a diene elastomer and the shell from a continuous layer from one

ERSATZBL _Ä TT (REGEL26) Methyl methacrylate resin, an acrylonitrile resin or a vinyl chloride polymer.

Although the first two shell materials meet the requirement for a chlorine-free polymer, polymer particles with a high proportion of hard shell material are required for storage-stable plastisols. Since these polymer components are at least partially incompatible with the plasticizer, heterodisperse systems are formed after the gelling process, which systems do not allow optimum performance properties to be achieved. Vinyl chloride polymer as the shell material reduces the chlorine content compared to pure PVC plastisols, but since these are not chlorine-free, these polymers represent only a less than satisfactory partial solution to the problem.

DE-A-40 34 725 describes that plastisol compositions with excellent application properties, in particular good storage stability, good adhesion to metals and high abrasion resistance and good mechanical properties, can be obtained if the organic polymer component can be prepared by emulsion polymerization Styrene copolymer powder uses which

a) styrene and / or α-methylstyrene and / or p-methylstyrene and b) 3 to 20% by weight (based on the copolymer) of methacrylic acid and / or acrylic acid and / or itaconic acid.

In the emulsion polymerization of these styrene copolymers, polymer particles with a very uniform average primary particle size of about 0.3 to 1.5 μm can be obtained, in which the polar carboxyl groups are essentially arranged on the outside and, as lipophobic residues, obviously for the stability of the dispersions of these particles in the plasticizer are responsible at room temperature. These copolymers have a molecular weight of the order of 200,000 to 1,000,000.

tRS _{Ä Ä} TZBL TT (REGEL26) The aqueous polymer dispersions are usually dried by spray drying processes. However, additional problems arise with chlorine-free polymers, since the very finely divided polymer powders tend to have dust explosions due to their very low minimal ignition energy. In order to eliminate this risk during drying, the chlorine-free polymer dispersions have to be spray-dried under inert conditions, but this process makes the polymer production process considerably more expensive. The object was therefore to provide chlorine-free polymer powders for use in plastisols which do not need expensive spray drying processes under inert conditions.

It has now been found that, after simple filtration and subsequent drying, and plasticizers and customary other additives, plastisols can be prepared from certain bead polymers, which are suitable as adhesives, sealants and / or coating compositions.

Pearl polymerization, often also called suspension polymerization, has long been known per se. In this process, it is known that the organic monomer, which is largely insoluble in water, is suspended in the aqueous phase with the aid of protective colloids and / or stabilizers as dispersion aids, and polymer particles of more or less size are formed. Water-insoluble inorganic salts are often used as protective colloids and / or stabilizers. Usually, these inorganic salts are separated and removed from the polymer during workup, e.g. B. by treatment with acids.

It has now been found that, surprisingly, the inorganic constituents can remain in the polymer, so that the workup process is particularly simple and therefore economical. The invention thus relates to plastisol compositions based on pearl polymers, which are filtered off from the aqueous phase after the polymerization without further processing and are then freed of the residual moisture in a conventional drying process.

The dispersing agents are selected so that they have at least no interfering influence in the plastiso composition, preferably they are at least in part normal components of the plastisol. The inorganic constituent of these dispersing agents - also called Pickering emulsifier - is therefore preferably barium sulfate, calcium carbonate, magnesium carbonate, calcium silicate or an aluminosilicate. In addition, ionic or nonionic emulsifiers are added in a minor amount, such as. B. sodium cetyl stearyl alcohol sulfate.

In principle, all monomers capable of free radical polymerization with low water solubility can be used for this suspension polymerization process, but styrene-methacrylic acid or styrene-acrylic acid copolymers as described in DE-A-4034725 are preferably used according to the above processes polymerized and used in the plastisols according to the invention. The monomers can either be initially charged or only the styrene is initially charged and the methacrylic acid or acrylic acid is metered in during the polymerization period. Due to the different solubility of the monomers in the polymer or water, a concentration gradient of the (meth) acrylic acid can be achieved over the particle cross section. This is desirable because on statistical average there are sufficient carbxyl groups in each polymer molecule for later crosslinking reactions and / or adhesion promotion. The particle size of the polymer can be varied within wide limits by suitable choice of the monomer concentration, the monomer / dispersant ratio and the stirrer speed and / or

ERS _Ä TZB π (RULE 26) geometry can be varied. The average particle size of the bead polymers for the plastisols according to the invention is between 1 μm and 150 μm, preferably between 5 μm and 60 μm.

The polymer formed can be separated from the water very easily by filtration and subsequent drying at 50 ° C. to 150 ° C., preferably at 60 ° C. to 100 ° C., and can be used directly for the production of plastisol, the inorganic residue remaining in the polymer Part of the dispersing agent serves as a filler which is necessary in the plastisol anyway. Since the above-mentioned drying process only serves to remove the residual moisture after the filtration, the less complex and therefore inexpensive belt drying processes or drying in a fluidized bed are suitable for this step. Surprisingly, the minimum ignition energy for these suspension polymers increases by a factor of about 1,000 in comparison to polymers which were produced according to DE-A-40 34 725 with the aid of the spray drying process. This is desirable because polymers with such a high minimum ignition energy can be handled safely without a great deal of inerting.

In addition to the previously mentioned comonomers, the comonomers mentioned in DE-A-4034725 can also be used, the comonomers mentioned there are expressly part of this application.

The plastiso composition according to the invention contains about 30 to 1,000 parts by weight of plasticizer per 100 parts by weight of the styrene copolymer. Conventional organic plasticizers are in themselves suitable as plasticizers (cf. Paul E. Bruins, Plasticizer Technology [Weinhold Publishing Corporation, New York], Volume 1, pages 228-232). Alkyl phthalates such as dibutyl phthalate, dioctyl phthalate, butyl benzyl phthalate, dibenzyl phthalate and very particularly diisononyl phthalate (DINP) are preferred. However, the known ones are also suitable

SPARE BLADE (RULE 26) Plasticizers from the group of organic phosphates, adipates and sebacates or also benzyl benzoate or diphenyl ether.

In addition to the additives mentioned so far, the plastisols according to the invention may also contain additives which are customary in plastisol technology. B. calcium carbonate in the form of various chalks, heavy spar, mica, vermiculite, pigments such. B. titanium dioxide, carbon black, iron oxides, blowing agents for the production of foamed plastisols, anti-aging agents, rheology aids such. B. pyrogenic silicas, bentones, castor oil derivatives.

The plastisols according to the invention are particularly suitable in motor vehicle construction as underbody protection agents and also as adhesives for relining the hood, as masses for sill protection and as spot welding pastes, and other adhesive applications. In the packaging industry, they can be used with advantage as sealants for container closures such as crown caps as well as seam sealants and seam seam adhesives for tin cans.

In addition, these plastisols can also be used for a variety of other technical applications, including: a. Coating aces for wallpaper, floor coverings, textile coating compositions, sheathing of panes, z. B. for Automob l- and other vehicle construction analogous to the method described in EP-B-333538, as an adhesive for the production of multi-pane safety gas.

The following examples are intended to illustrate the invention:

ERSAΓZBLÄΓT (RULE 26) Examples

The polymerization reaction takes place in a stirred tank (R) which is equipped with a stirrer consisting of three MIG stages and baffles. The stirrer speed is infinitely adjustable. A container (V) is used as a template. The template is weighed and connected to the reactor R via a stainless steel line. The dosing takes place automatically by preselecting the corresponding dosing rate. The reactor R has various heating or cooling circuits. The system can be operated in a temperature range from 15 ° C to 120 ° C via two separate temperature sensors (product temperature) installed in R. Nitrogen can be passed over to produce an inert atmosphere in the reactor R.

Water, styrene, initiator and emulsifier are placed in the reactor. After the heating phase to the reaction temperature (80 to 90 ° C.), the polymerization begins by thermal decomposition of the peroxide used.

The metering of the methacrylic acid from template V into the reactor is controlled gravimetrically and takes place within the first three to four hours of the reaction. The total reaction time is 7 to 8 hours.

The excess heat of reaction is removed by tempering the reactor with mixed water.

The present process is a simple radical copolymerization of styrene with methacrylic acid in an aqueous suspension with a water content of approx. 50%. The polymerization is initiated by dibenzoyl peroxide or similar initiators which are poorly soluble in water by thermal radical formation.

ERSAΓZBLAΓT (RULE 26) After the reaction has ended, the dispersion is cooled (<45 ° C.) and discharged through a belt filter. The residual moisture is removed by a downstream dryer. The powder obtained can be used directly for the production of plastisol; storage-stable plastisols are formed.

Example 1: Polymerization formulation A (21 system)

Weigh out parts by weight

Water 750.0 g 44.2%

Styrene 750.0 g 44.2%

Methacrylic acid 45.0 g 2.6%

Barium sulfate 150.0 g 8.8%

Dibenzoyl peroxide 3.8 g 0.2%

Lanette E 0.1 g

Stirrer speed: 500 min ---

Response time: 450 min

Water, barium sulfate and Lanette ER (sodium cetyl stearyl alcohol sulfate) are placed in a 2 1 double-jacketed vessel which is equipped with a reflux condenser and a three-stage MIG stirrer (diameter 90% of the inside diameter of the reactor). The initiator dibenzoyl peroxide is dissolved in the styrene. This solution is completely added to the reactor with stirring (defined stirrer speed). The reaction mixture is rendered inert by passing nitrogen over it. The reaction temperature is raised to within 30 minutes. When the reaction temperature has been reached, the methacrylic acid metering is started. The comonomer is metered evenly within 3 hours. The course of the reaction is about

ERSrZBLIT ^ ^SEL26) gravimetric solids determination followed. The polymerization is complete after a total of 7.5 h. The solid is filtered off on a suction filter and dried at approx. 50 ° C.

analytical data:

Particle size: X50 = 38 μm,

Molar mass: Mw = 136000; M _n = 48000.

Example 2: Polymerization recipe B (251 plant)

Weigh out parts by weight

Water 12000.0 g 61.3%

Styrene 6000.0 g 30.6%

Methacrylic acid 360.0 g 1.9%

Barium sulfate 1 200.0 g 6.1%

Dibenzoyl peroxide 24.0 g 0.1%

Lanette E 1.2 g

Stirrer speed: 300 min " ¹

Response time: 450 min

The reaction takes place analogously to Example 1 in a double-walled glass reactor, which is also equipped with a three-stage MIG stirrer (90% of the reactor inner diameter). The stirrer speed corresponds to the same peripheral speed as with the 2 1 approach.

analytical data:

Particle size: X50 = 106 μm,

Molar mass: Mw = 316000; M _n = 107,000.

ERSATZBL _Ä TT (REGEL26) Example 3: plastisol formulation

Weighing parts by weight

SMA polymer from Example 1 *) 41.6 g 43.9%

Barium sulfate 4.4 g 17.2%

Diisononyl phthalate 22.5 g 29.9%

Aerosil 200 0.3 g 0.4%

Versamid 140 1.5 g 2.0%

Dicycloheptyl phthalate 5.0 g 6.6%

*): The weighed-in SMA polymer consists of 79% polymer and 11% barium sulfate (according to the polymerization recipe)

The plastisol is made according to the above. Composition prepared in a beaker and homogenized.

To check the storage stability, viscosity measurements were carried out on the CARRI-MED CS rheometer (plate / plate; 0 = 4 cm): Measurements of the freshly prepared plastisol and after three days at 25 ° C. gave practically identical values for the viscosity in Pas in Dependent on the shear rate in (1 / sec).

No significant gelation was observed. After applying a film (400 μm) to a sheet and then tempering (15 min

REPLACEMENT BLAπ (RULE 26) at 160 ° C) homogeneous, optically appealing and mechanically stable (visual assessment) coatings were obtained.

Claims

Patent claims 1. Plasticisis composition based on pearl polymer. 2. Plastisoi composition according to claim 1, characterized in that the polymer particles of the or the bead polymer (s) have a core / shell structure. 3. Plastisoi composition according to claim 1 and / or 2, characterized gekenn¬ characterized in that the polymer is chlorine-free. 4. Plastisoi composition according to at least one of claims 1 to 3, characterized in that the primary particles of the or the Perlopolymerisate have an average diameter of 1 to 150 microns, preferably from 5 to 60 microns. 5. Plastisoi composition according to claim 1 to 4, characterized gekennzeich¬ net that as a copolymer, a copoly eres containing a) styrene and / or α-methylstyrene and / or p-methylstyrene and b) 2 to 20 wt .-% (based on the Copolymers) olefinically unsaturated carboxylic acids, e.g. B. methacrylic acid and / or acrylic acid and / or itaconic acid and c) optionally further crosslinking co-monomers is used. 6. Plastisoi composition according to claim 1 to 5, characterized gekennzeich¬ net that as a dispersant is a water-insoluble inorganic ERSÄΓZBLÄΓT (RULE 26) Salt and an ionic and / or nonionic emulsifier is used. 7. Plastisoi composition according to claim 1 to 6, characterized gekennzeich¬ net that it a) 5 to 50 wt .-% of the bead polymer, b) 5 to 60 wt .-% of a plasticizer, c) 5 to 40 wt .-% fillers d) 0 to 10% by weight of an adhesion promoter e) 0 to 10% by weight of a crosslinking agent f) 0 to 10% by weight of a rheological aid g) up to 5% by weight of further customary additives and / or auxiliaries for Contains plastisols. 8. Plastisoi composition according to claim 1 to 7, characterized gekennzeich¬ net that the bead polymer is separated after the polymerization by filtration from the aqueous phase and then dried at about 50 ° C to 150 ° C. 9. Use of a Plastisoi composition according to one of claims 1 to 8 in motor vehicle construction as an underbody protection agent, as an adhesive for the hood relining, as a mass for sill protection, as a metal adhesive or as a spot welding paste. 10.Use of a plastisoi composition according to one of claims 1 to 8 in the packaging industry as a sealing compound for container closures or as a seam sealing agent or as a seam seam adhesive for tin cans. REPLACEMENT BLAπ (RULE 26) 11.Use of a plastiso composition according to at least one of claims 1 to 8 for coating textiles, wallpapers or floor coverings. 12.Use of a plastiso composition according to at least one of claims 1 to 8 for sheathing panes, in particular for the automotive industry. 13.Use of a plastisoi composition according to at least one of claims 1 to 8 for the production of floor coverings. SPARE BLADEBL (RULE26)