CS239984B1 - Mixtures with enhanced adhesion to substrates based on polyvinyl chloride - Google Patents

Abstract

The solution relates to polymer mixtures based on polyvinyl chloride plastisols. The mixtures are characterized by the content of at least two different types of PVC, one of which has an increased ability to absorb plasticizers characterized by a plasticizer absorption time under standard conditions in the range of 4-14 minutes, while the ratio of the amount of PVC with the stated absorption capacity to the other polymers is 0.2:1 to 4:1. PVC with increased absorption capacity reduces the amount of free plasticizer in the mixture, thereby increasing adhesion to various substrates while maintaining rheological properties, especially viscosity, necessary for technological reasons. Other advantages of the mixtures according to the invention are also shorter times and lower gelation temperatures.

Description

The invention relates to polymer mixtures based on polyvinyl chloride with improved adhesive properties. After heat treatment, the mixtures are intended for protective coatings of steel sheets, fittings, profiles and their joints.

It is known that the adhesion of gelatinized mixtures of vinyl polymers to various surfaces depends _on the concentration of free plasticizer in the mixture at the time when adhesion is formed. Regardless of the type of plasticizer or substrate, adhesion increases with increasing concentration up to a certain maximum. With a further increase in the plasticizer content, adhesion decreases, both due to a decrease in the cohesive strength of the coating and a decrease in the area of contact between the polymer and the substrate.

When choosing the composition of mixtures, especially the content of plasticizer, it is not possible to follow only the described connections with respect to the adhesion of the coating. The mixtures are most often applied by spraying or atomizing. The condition for the satisfactory progress of these technological operations is certain values of the rheological properties, especially viscosity. In practice, reducing the viscosity to the required value usually requires using such a high amount of plasticizer in the mixture that it is already beyond the maximum dependence of the adhesive strength on the plasticizer concentration. This deficiency can only be partially eliminated by gelation with a high content of plasticizers at higher temperatures and for a longer time, which, however, entails a prolongation of the entire process and an increase in energy costs.

The aim of this invention is therefore to find plastisol coating mixtures that would suitably meet both the technological requirements of the processing procedures and the requirements for the quality of the gelatinized coating itself, in particular its sufficient adhesion.

It has now been found that this aim of the invention is essentially met by mixtures which essentially contain 10-50% by weight of at least two types of polyvinyl chloride, at least one of which has a plasticizer absorption time under standard conditions of from 4 to 14 minutes, the ratio of the amount of polyvinyl chloride with the stated absorption capacity to polyvinyl chloride with a different absorption capacity being 0.2:1 to 4:1 /3 preferably 0.4:1 to 2:1 and further 20-70% by weight of a plasticizer or a mixture of ester-type plasticizers, 0.1-70% by weight of a filler, 0.1-6% by weight of an adhesive additive and 0.1-10% by weight of other conventional additives such as pigments, stabilizers or blowing agents.

The plasticizer absorption time under standard conditions is understood here as the time determined by the method according to ASTM D 2396-69. The powdered vinyl polymer is mixed in a Brabender plasticizer kneader and, after preheating at 93 °C, dioctyl phthalate is added. A wet lumpy mixture is formed, which changes into a free-flowing powder. The transition from the wet lumpy state to the dry powder state is accompanied by a rather significant change in the torque. The time of formation of the dry powder, i.e. the time from the addition of dioctyl phthalate to the point where the mixture changes into a dry powder state, characterizes the absorption rate of vinyl polymers. A typical time for the absorption rate of vinyl polymers with a high plasticizer binding ability is in the range from 4 to 14 minutes, especially from 4 minutes to 10 minutes. Vinyl polymers that do not have an increased ability to absorb plasticizers do not exhibit the described change in torsional moment.

Polymers with increased plasticizer absorption capacity are used to prepare plasticized dry mixes processed by extrusion.

When used in gelling mixtures, this type of polymer is used for its ability to bind the plasticizer in such a way that

239 984 at the beginning of the gelatinization process, rapid absorption and reduction of the free plasticizer content in the mixture will occur. Since the adhesive properties of the mixture are related to the free plasticizer content, the adhesion value will approach the maximum values _, even with a higher total plasticizer content in the mixture. At the same time, the conditions for the formation of the adhesive bond will be favorably influenced by lower temperatures and shorter gelatinization times.

The preferred mutual weight ratio of the various vinyl polymers is given by the ratio of the weight of the polymers with increased absorption capacity to the weight of the other polymers and is in the range from 0.2:1 to 4:1, preferably 0.4:1 to 2:1.

To further clarify the nature of the invention, we present the following examples:

Example 1

Mixture

A B

Polyvinyl chloride paste 18.00 10.00 Polyvinyl chloride with increased absorption (absorption rate 8.5 minutes according to ASTM D 2396-69) 0 8.00 Dioctyl phthalate 25.85 25.85 2,2,4-trimethyl-1,3-pentanediol diisobutyrate 4.00 4.00 tribasic lead sulfate 0.35 0.35 resorcinol 0.35 0.35 hexamethylenetetramine 0.15 0.15 silicon dioxide 0.75 0.75 calcium carbonate 48.55 48.55 calcium oxide 2.00 2.00

239,984

The adhesion of polyvinyl chloride mixtures A and B to raw, non-degreased steel sheet was evaluated by a peel test on a 10 mm wide strip after gelation:

a) at temperatures of 140, 150 and 160 °C and a gelation time of 15 minutes A B

140°C 150°C 160°C

b) at temperature easy peeling easy peeling cannot be peeled cannot be peeled cannot be peeled

120, 130 and 140 °C and a gelation time of 30 minutes

120°C 130°C 140°C

And easy peel easy peel can't peel

B cannot be peeled cannot be peeled cannot be peeled

For mixture A without the polyvinyl chloride combination, adhesion to the substrate was achieved at a gelation temperature of 160 °C in 15 minutes or at a gelation temperature of 140 °C in 30 minutes, while for the same comparative mixture B with the combination according to the invention at gelation temperatures 20 °C lower, i.e. in 15 minutes at a gelation temperature of 140 °C in 30 minutes at a gelation temperature of 120 °C. At the same gelation temperature/e.g. 140 °C, adhesion to the substrate was achieved for mixture A in 30 minutes and for mixture B in 15 minutes.

Example 2

Mixture

C D Polyvinyl chloride paste 18.00 10.00 Polyvinyl chloride with increased absorption. (absorption rate 8.5 minutes according to ASTM D 2396-69) 0 8.00 Dioctyl phthalate 26.00 26.00 2,2,4-trimethyl-1,3-pentanediol diisobutyrate 4.00 4.00 silicon dioxide 0.50 0.50 amine amide resin 1.00 1.00 calcium oxide 1.00 1.00 calcium carbonate 49.50 49.50

239,984

The adhesion of mixtures C and D to the electrophoretic basecoat was evaluated by a peel test on a 10 mm wide strip after gelation:

a) at temperature

140°C 150°C 160°C

b) at temperature

120°C 130°C 140°C

140, 150 and 160 °C and a gelation time of 15 minutes C D

120, easy peeling not possible easy peeling not possible peeling very difficult not possible

130 and 140 °C and a gelation time of 30

C D peel off peel off peel off minutes easy peel off easy peel off cannot peel off cannot peel off cannot peel off

For mixture C without the polyvinyl chloride combination, adhesion to the substrate was achieved at a gelation temperature of 160 °C in 15 minutes, or at a gelation temperature of 140 °C in 30 minutes, while for the same comparative mixture D with the combination according to the invention at gelation temperatures 20 °C lower, i.e. in 15 minutes at a gelation temperature of 140 °C and in 30 minutes at a gelation temperature of 120 °C. At the same gelation temperature, e.g. 140 °C, adhesion to the substrate was achieved for mixture C in 30 minutes and for mixture D in 15 minutes.

Example 3

Mixture

E F

Polyvinyl chloride paste 22.00 14.00 Polyvinyl chloride with increased absorption (absorption rate 4.5 minutes according to ASTM Ď 2396-69) 0 8.00 Dioctyl phthalate 35.00 35.00 Calcium carbonate 40.00 40.00 Ca/Zn stabilizer 0.65 0.65 Resorcinol 0.50 0.50 Hexamethylenetetramine 0.35 0.35 Calcium oxide 1.50 1.50

239,984

The adhesion of mixtures E and F to raw, non-degreased steel sheet was evaluated by a peel test on a 10 mm wide strip after gelation at temperatures of 140, 150, 160 and 170 °C and a gelation time of 20 minutes:

E F 140°C easy peel exfoliation very difficult 150°C easy peel cannot be peeled off 160°C exfoliation difficult cannot be peeled off 170°C cannot peel cannot be peeled off

For the mixture without the polyvinyl chloride combination, adhesion was achieved at a gelation temperature of 170 °C in 20 minutes, while for the same comparative mixture F e with the combination according to the invention at a temperature 20 to 30 °C lower.

Claims (1)

Mixtures with increased adhesion to polyvinyl chloride-based substrates, characterized in that they contain 10-50% by weight of at least two types of polyvinyl chloride, at least one of which has a plasticizer absorption time under standard conditions of from 4 to 14 minutes, the absorbency to polyvinyl chloride having a different absorbency is 0.2: 1 to 4: 1, preferably 0.4: 4 to 2: 1, and 20-70% by weight of an emollient or ester-type plasticizer mixture, 0.1-70% by weight % filler, 0.1-6% by weight adhesive and 0.1-10% by weight other conventional additives such as pigments, stabilizers or blowing agents *