CS236243B1 - Mixtures for pastes on base of polyvinylchloride or copolymers of vinyl chloride - Google Patents

Abstract

Srn chlori ro pastes pastes based on vinyl chloride copolymers with pseudoplastic flow behavior containing as an active substance for increasing the viscosity 0.01 - 10 parts by weight of an aqueous dispersion of polymers or copolymers miscible with polyvinyl chloride in 100 parts by weight of the paste. Aqueous dispersions of the following polymers and copolymers can be used: ÍS1 tíu ne - polyvinyl chloride and vinyl chloride copolymers - polyvinyl acetate. and vinyl acetate copolymers - copolymers based on acrylic acid esters. The dispersions contain 40 - 60% by weight of water. At dosages higher than 0.5 parts by weight of dispersion per 100 parts by weight of paste, water is removed from the paste by adding alkaline earth metal oxides, preferably CaO, in an amount of 0.1 - 40 parts by weight per 100 parts by weight of paste or molecular sieves, which bind the water added to the paste in the form of a dispersion.

Description

The invention relates to a mixture for pastes based on polyvinyl chloride or vinyl chloride copolymers containing a polymer, a plasticizer and optionally other substances from the group of common additives.

The basic components of polyvinyl chloride plastisols are the paste-forming polyvinyl chloride, or its copolymers, and a plasticizer. For various purposes, these basic components are supplemented with a number of other additives such as fillers, stabilizers, pigments, kickers, blowing agents, adhesive additives, viscosity regulators, etc. In general, a paste mixture for 100 parts by weight of polyvinyl chloride contains 30-300 parts by weight of plasticizer, 0-300 parts by weight of filler, and 0-50 parts by weight of some of the additives from the group including stabilizers, pigments, blowing agents and activators of their decomposition, viscosity regulators, and surfactants, or combinations thereof.

Polyvinyl chloride pastes have a wide range of applications. Currently, vinyl coating soles are used for the production of flooring, leatherette, conveyor belts, protective sprays and anti-corrosion coatings, cast and dipped products, etc.

For some plastisol processing technologies, pseudoplastic flow behavior of the paste is required. This means that the paste must be fluid under shear stress; at rest, its viscosity must be high. For example, in the production of leatherette, polyvinyl chloride paste is applied to textiles. The paste must flow very smoothly under the coating knife so that the applied layer is uniform. Behind the knife, when the paste is at rest, it must be sufficiently viscous to prevent the paste from penetrating the textile and thus causing undesirable stiffening of the entire structure.

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Currently, several methods are known for increasing viscosity and pseudoplasticity in paste-forming types of polyvinyl chloride:

1. use of rapidly solvating plasticizers (e.g. dibutyl phthalate)

2. addition of fillers with a large specific surface area (e.g. pyrogenic SiO2)

3. adding substances that accelerate the disintegration of polyvinyl chloride particles (e.g. butyl acetate).

The effectiveness of fast-solvating plasticizers is sufficient only after the paste has been left to stand for several hours. These plasticizers are also characterized by high volatility and migration from the finished product. Fillers with a large specific surface area affect the rheological behavior of the paste by creating weak bonds and structures at rest.

These bonds break down quickly as a result of shear stress, which causes a decrease in the viscosity of the polyvinyl chloride paste. The disadvantage of pyrogenic silica, which has been most often used for this purpose so far, is its large volume requiring large storage spaces and high dustiness during weighing and dosing. Solvents accelerating the breakdown of polyvinyl chloride particles are also sufficiently effective only after the paste has been left to stand for several hours; given that these are mostly flammable substances 1. and

2nd class, the demands on storage conditions and work safety increase.

The shortcomings of the previously known methods for increasing the viscosity and pseudoplasticity of polyvinyl chloride paste are eliminated by the use of mixtures according to the invention, the essence of which is that they contain as an active substance for increasing the viscosity 0.01-10 parts by weight of an aqueous dispersion of polymers or copolymers miscible with polyvinyl chloride in 100 parts by weight of the paste. The average particle size of these dispersions ranges from 0.1-0.5 microns. Aqueous dispersions of the following polymers and copolymers can be used:

- polyvinyl chloride and copolymers of vinyl chloride

- polyvinyl acetate and vinyl acetate copolymers

- copolymers based on acrylic and/or methacrylic acid esters

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After adding the dispersion to the polyvinyl chloride paste, these particles swell very quickly with the plasticizer, which leads to a sharp increase in viscosity and an emphasis on the pseudoplastic flow character. The dispersions mentioned contain 40-60% by weight of water. At dosages higher than 0.5 parts by weight of the dispersion per 100 parts by weight of the polyvinyl chloride paste, water is removed from the paste to avoid defects in the finished product. For this purpose, alkaline earth metal oxides, preferably calcium oxide, or molecular sieves are added to the paste, which bind the water added to the paste in the form of a dispersion. The molecular sieves are filtered out of the paste.

Compared to previously used methods of increasing the viscosity and pseudoplasticity of polyvinyl chloride paste according to the invention, it has the following advantages:

- the polymers and copolymers used do not migrate from the finished product and do not volatilize at processing temperatures,

- have high efficiency in a short time after mixing the paste,

- do not require large storage spaces,

- easy to dose,

- they are non-flammable.

The following examples are intended to further clarify the nature of the invention:

Example 1

To demonstrate the effect of individual dispersions on the pseudoplasticity of polyvinyl chloride paste, the following mixtures were prepared:

paste-forming polyvinyl chloride 100 parts weight dioctyl phthalate 67 II II organotin stabilizer 0.5 ff ff aqueous polymer dispersion 2.0 II II CaO (1:1 masterbatch in dioctyl phthalate) 6.0 II II

The following substances were used as aqueous polymer dispersions:

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Sokrat 2 804 - dispersion based on styrene copolymer with acrylic acid esters

Sokrat 942 - dispersion based on copolymers of acrylic and methacrylic acid esters with non-acrylic monomers and containing thickening monomers

Duvilax BD-20 - polyvinyl acetate dispersion

Polyvinyl chloride latex

The mixtures were mixed in a laboratory mixer for 10 minutes at

1000 rpm. The viscosities of the pastes were measured with a Brookfield spindle viscometer No. 6 at 0.5 and 20 rpm. The pseudoplasticity factor is given as the ratio of the viscosities measured at 0.5 and 20 rpm.

Table 1

Mixture revolutions min viscosity mPas after preparation after 24 hours pseudoplasticity factor after preparation after 24 hrs. Standard 0.5 5 o o o 20 000 1.02 1.25 20 4 900 16 000 Socrates 2,804 0.5 8 000 88 000 0.68 2.01 20 11 700 43 800 Socrates 942 0.5 38 000 120 000 1.71 1.94 20 22 200 ⁶¹ 800 Duvilax BD-20 0.5 12 500 35 200 1.39 1.97 20 9 000 17 900 latex PVC ' 0.5 14 000 52 000 1.5 2.11 20 9 300 24 000

Example 2

This example shows a mixture for lightweight layers of flat structures.

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Mixture composition mixture no.1 mixture no.2 paet-forming polyvinyl chloride 100 100 di-2-ethylhexylphthalate 63.4 63.4 organotin stabilizer 0.5 0.5 Socrates 942 0 2.0 CaO (1:1 masterbatch in dioctyl phthalate) 9.5 9.5 Aerosil 200 1.5 1.5 color premix 0.25 0.25 blowing agent (azodicarbonamide) 2.0 2.0 blowing agent decomposition activator 1.0 1.0

(organic complex compound Cd-Zn)

The preparation of the pastes and the viscosity measurements were identical to Example 1. The effect of the dispersion (Sokrat 942) is evident from Table 2.

Table 2

Mixture speed min1 viscosity mPas pseudoplasticity factor after preparation after 24 hours after preparation after 24 hours No. 1 0.5 43,300 52,000 3.31 3.82 20 13,650 13,600 No. 2 0.5 84,000 190,000 3.20 4.62 20 26,250 41,100

Claims (2)

SUBJECT OF THE INVENTION 238 243 1. Mixtures for pastes based on polyvinyl chloride or vinyl chloride copolymers comprising a polymer, a plasticizer and, optionally, other substances from the group of conventional additives such as fillers, stabilizers, pigments, kikers, blowing agents, viscosity regulators, characterized in that they contain 0.01 parts by weight of paste up to 10 parts by weight of an aqueous dispersion of polymers or copolymers selected from the group consisting of polyvinyl chloride and vinyl chloride copolymers, polyvinyl acetate and vinyl acetate copolymers and copolymers based on acrylic or methacrylic acid esters and optionally further comprising alkaline earth oxides, preferably calcium oxide. 2. Mixtures according to claim 1, characterized in that they contain alkaline earth oxides in an amount of 0.01-40 parts by weight per 100 parts by weight of the polyvinyl chloride paste.