NO143404B - APPLICATION OF POLYVINYL CHLORIDE PREPARED IN A PARTICULAR MANNER FOR THE PREPARATION OF SOFT FOAMS - Google Patents

Description

It is known to produce emulsifier-containing polyvinyl chloride by continuous polymerization in emulsion. Work is carried out in the presence of water-soluble catalysts and usually in the presence of ionic emulsifiers such as alkyl sulphonates, alkyl aryl sulphonates, alkyl sulphates and alkali salts of fatty acids.

The further processing of the thus prepared polymer dispersion usually takes place by spray drying, during which a fine-grained powder is produced that can be processed with plasticizers into pasty, moldable masses, so-called pastes or plastisols. There are different processing processes for pastas, e.g. casting processes (rotational casting), dipping methods and coating methods.

A special place is occupied by the production of soft polyvinyl chloride foam by the coating method. A leavening agent such as e.g. azodicarbonamide. At the high temperatures in the gelling channel, the blowing agent decomposes, and the paste is foamed and gelled at the same time. A soft foamy substance is formed below. This method has a wide range of applications, especially in the production of artificial leather.

In this method, two properties of the coated foam are of great importance. Firstly, the viscosity of the paste before gelation must be as low as possible, and secondly, it is required that, even with the shortest residence time (approx. 1.3 minutes) in the gelation channel, a foamed product with a fine, regular pore structure, low mass density and smooth surface.

So far, it has not been possible to satisfy both of these requirements at the same time.

In the known use of alkylsulfonate as an emulsifier in the production of polyvinyl chloride which is capable of forming pastes (see US-PS 2 727 627), pastes with good viscosity ratios are indeed obtained, but with short residence times in the gelling channel it is not possible to produce some foam material, as shown in example 5.

If alkyl sulfate is used as an emulsifier during the polymerization in a known manner (see FR-PS 977 296), a foam with satisfactory properties is obtained from the paste produced from this polymer, even with short residence times of 1.3 minutes, but the viscosity properties of the paste are completely inadequate, as can be seen from the results in Example 7.

These disadvantages of the state of the art are overcome by

that for the production of soft polyvinyl chloride foams according to the coating method using chemical foaming agents, a polyvinyl chloride produced by continuous polymerization in emulsion in the presence of water-soluble catalysts and emulsifiers and 1.6 - 2.8 percent by weight, calculated on the monomers, of an emulsifier system is used of

a) 70-30 percent by weight of an alkyl sulfate with the formula R -OSO^Me, where R is an alkyl residue with 10-18 carbon atoms and Me is Na

or K,

b) 0-65 percent by weight of an alkyl ether sulfate with the formula

R - (OCH2 - CH2)n - OS03Me, where n stands for an integer from

1 to 5 and R and Me have the meaning stated above, and

c) 0-60% by weight of a Na-alkyl sulphonate whose alkyl chain carries 10-20 carbon atoms,

with components a, b and c together making up 100 percent by weight.

According to a preferred embodiment, an emulsifier system of

60-33 1/3 weight percent of component a)

30-33 1/3 weight percent of component b) and

10-33 1/3 weight percent of component c) .

In a special embodiment, an emulsifier system is used

35-65 percent by weight of component a) and

65-35 percent by weight of component b).

In a further special embodiment, an emulsifier system is used

40-60 percent by weight of component a) and

60-40 percent by weight of component c).

GB-PS 9 52 356 describes a production of polyvinyl

chloride in the presence of a sulfate or an ether sulfate (see claim 1).

When an ether sulphate is used, it should not be used

a sulfate as indicated under a) above. Above all, however, the British patent does not contain any instructions for using the produced polyvinyl chloride for the production of foams.

The patent document cannot therefore make the present invention proximate.

US-PS 3 546 193 describes the use of either alkyl sulphate or alkyl sulphonate in the production of polyvinyl chloride, while there an ester of a sulphocarboxylic acid is always added as a second emulsifier (see column 2, lines 10 to 29). This means that only one of the emulsifiers in the combination required according to the invention is present. In addition, this patent does not contain any reference to the fact that the polyvinyl chloride is to be used for the production of foams. Nor can this patent specification therefore make the present invention proximate.

The polymers produced according to the invention can be advantageously used for the production of soft foams by the coating method using chemical foaming agents. The products obtained in this way show a good to excellent viscosity of the pastes and even with short residence times in the gelling channel (1.3 minutes) give foam substances with satisfactory to very good foam properties.

Alkyl sulphates which according to the invention can be used as emulsifiers are e.g. Na-decyl sulfate, Na-lauryl sulfate, Na-tetradecyl sulfate, Na-cetyl sulfate, Na-stearyl sulfate. For reasons of availability, however, one will often not use these substances individually, but use the sodium salts of the sulfates of mixtures of c^q - C^g alcohols. It is advantageous to use mixtures in which lauryl sulphate is present in a predominant quantity.

The sodium salt of lauryl ether sulfates is preferably used as alkyl ether sulfate. The number of ether groups is 1-5, preferably 2-3. Examples are Na-lauryloxetyl sulfate, Na-lauryldioxetyl sulfate, Na-lauryltrioxetyl sulfate, Na-lauryltetraoxetyl sulfate, Na-laurylpenta-oxetyl sulfate. Corresponding ether derivatives can be derived from Na-decyl sulphate, Na-tetradecyl sulphate, Na-cetyl sulphate and Na-stearyl sulphate. For economic reasons, alcohol mixtures with a carbon number of 10-18 are often used as starting material for the production of these compounds. Preferably, such starting mixtures contain lauryl alcohol in a predominant amount.

The Na salts of alkylsulfonates to be used according to the invention are sodium salts of sulfonates of hydrocarbons with 10-20 carbon atoms, such as decane, dodecane, heptadecane, hexadecane and octadecane. In general, for sulfoxidation resp. sulfochlorination use mix-

things, preferably those that have a maximum at C, .- - C-, r.

15 16

A description of the preparation of the sulphonates can be found in

F. Asinger Chemie und Technologie der Paraffin-Kohlenwasser-

substances, Akademie-Chemie Berlin, 1956, pages 453 - 465.

During the polymerization, the pH value must be between 3 and 9, preferably between 5 and 7. Different buffer substances can be used to adjust the pH value, e.g. alkali phosphate or sodium acetate.

The concentration of the buffer substance can amount to 0.001 - 1.0%, preferably 0.01 - 0.5%, calculated on vinyl chloride.

The emulsifiers and buffer substances are dissolved in completely desalted water, so that the solids content (of emulsifier and buffer substance) in the water amounts to 1.6 - 2.5%, preferably 1.9 - 2.3%. The emulsifier content amounts to 1.6 - 2.8 weight percent, preferably 1.9 - 2.6 weight percent, calculated on vinyl chloride. The phase ratio (based on the volume) between vinyl chloride and emulsifier water amounts to 1:0.7 - 1:2. Usually, one tries to set the phase ratio so that the solids content in the dispersion amounts to more than 48% by weight.

The polymerization is carried out with the well-known water-soluble activators. Preferably, potassium persulphate or ammonium persulphate is used with and without a reducing agent. It can also be polymerized with hydrogen peroxide and a reducing agent such as ascorbic acid.

The concentration of potassium persulphate can amount to 0.001 - 1%, preferably 0.01 - 0.5%, calculated on vinyl chloride. The concentration of α2°2 is 0/001 - 0.02%, preferably 0.01 - 0.02%. The activators are added as aqueous solutions.

The solution of emulsifier in water, the so-called emulsifier water, vinyl chloride and activator solution is continuously added to the polymerization boiler, so that an average residence time of approx.

6-7 hours.

The polymerization temperature is 40-60°C and the corresponding pressure 4-6 ato depending on the desired molecular weight of the polymer.

Further processing of the dispersion takes place by spray drying.

Example 1 (according to the invention)

The polymerization took place continuously in a 3 m 3 autoclave. The following amounts were added:

Vinyl chloride: 210 l/h

Emulsifier water: 183 l/h

Composition of the emulsifier water:

1.2% lauryl sulfate

0.6% lauryl ether sulfate

0.2% alkyl sulfonate (chain length of the alkyl residue C, o - <C>2<q> with a maximum at C,r - C~„)

lo £ u

0.1% Na acetate

The rest water

Activator: 2.0 l/h (3% solution of K2S20g in water) Polymerisation temperature: 50°C

Polymerization pressure: approx. 5 ato

Solid content in the dispersion: 48%

K-value: 70

Further processing of the dispersion took place in a spray drying plant. The inlet temperature of the drying air was approx. 160°C and the temperature at the exit of the tower 60°C. Otherwise, further processing took place as described in DT-OS 2 146 753.

The viscosity of the paste was measured with a viscometer from

company Haake on a plasticizer batch with 65 parts polyvinyl chloride powder and 35 parts dioctyl phthalate. The results were as follows:

To test the foaming properties and the polyvinyl chloride foam, a paste was prepared with the following composition:

100 parts polyvinyl chloride

54 parts dioctyl phthalate

30 parts benzyl butyl phthalate

3 parts azodicarbonamide

2 parts Cd/Zn stabilizer

1 part TiO

After a storage time of 18 hours, the pastes were coated on a "Release-Paper" and gelled and expanded in a nozzle gelling channel while changing the residence time and temperature.

The bulk density, pore structure and surface of the PVC foam were assessed.

At a foaming temperature of 200°C, the following results were obtained:

Residence time: 2 minutes 1.3 minutes

Mass density, g/cm 3: 0.26 0.32

Pore structure: fine pore fine pore

As will be seen, according to the invention, both excellent paste viscosities and good foam properties are achieved with the very short residence time of 1.3 minutes, which is technically of great interest.

Example 2 (according to the invention)

It was polymerized and further processed as in example 1. However, the emulsifier water had the following composition: 0.66% lauryl sulfate, 0.66% lauryl ether sulfate, 0.66% alkyl sulfonate (chain length of the alkyl residue C^g - C^q with a maximum at C^ ^ - C2q); 0.1% Na-acetate, the rest water.

The paste viscosity was measured as in example 1:

The foaming properties were tested as in example 1: Residence time: 2 minutes 1.3 minutes

Mass density, g/cm 3: 0.26 0.31

Pore structure: fine pore medium pore

With very good paste viscosities, foam with a regular structure is obtained which cannot be called distinctly fine-pored only with the very shortest residence time of 1.3 minutes.

Example 3 (according to the invention)

There was polymerisation and further processing as in example 1. The emulsifier water had the following composition: 1% lauryl sulphate, 1% lauryl ether sulphate, 0.1% Na acetate, the rest water.

The paste viscosity was measured as in example 1:

The foaming properties were tested as in example 1:

With a satisfactory viscosity of the paste, foam with very good properties was obtained, even with the shortest residence time.

Example 4 (according to the invention)

There was polymerisation and further processing as in example 1. The emulsifier water had the following composition: 1% lauryl sulphate, 1% alkyl sulphonate (chain length of the alkyl residue C^q - C20 with a maximum at C^q - C15), 0.1% Na acetate, the rest water.

The paste viscosity was measured as in example 1:

The foaming properties were tested as in example 1:

Satisfactory paste viscosities were achieved and, even with the shortest residence time, foam with satisfactory properties.

Example 5 (comparison example)

It was polymerized and further processed as in example 1.

However, the emulsifier water contained only 2% alkylsulfonate with a C fraction of C^q - C2q with a maximum at - C20* The paste viscosity was measured with a viscometer from the company Haake on a plasticizer batch with 60 parts PVC powder and 40 parts dioctyl phthalate.

The storage devices were tried as in example 1:

According to the state of the art, the paste viscosities are indeed good, but with the technically significant short residence times, no foam is obtained from the paste.

Example 6 (comparison example)

There was polymerisation and further processing as in example 1. However, the emulsifier water only contained 2% lauryl sulphate and 0.1% Na acetate.

The paste viscosity was measured as in example 1:

The foaming properties were tested as in example 1:

It turned out that the foam properties were indeed satisfactory, but that the viscosity ratios were completely inadequate.

Example 7 (comparison example)

There was polymerisation and further processing as in example 1. However, the emulsifier water contained only 2% lauryl ether sulphate and 0.1% Na acetate.

The paste viscosity was measured as in example 1:

The foaming properties were tested as in example 1:

The result is that the paste viscosity was indeed satisfactory, but that the foaming properties were insufficient.

Example 8 (comparison example)

It was polymerized and further processed as in Example 1. However, the emulsifier water had the following composition: 1.6% lauryl ether sulfate (80% by weight), 0.40% lauryl sulfate, 0.1% Na acetate and the remainder water.

The paste viscosity was measured as Example 1:

The foaming properties were tested as in Example 1:

It thus turned out that according to GB-PS 9 52 356 you get a polyvinyl chloride which only leads to foam with poor foam quality. In the aforementioned patent, there is thus no indication that the plastisols obtained are to be processed into foam.

As the emulsifier system therefore contains a maximum of 65% by weight of alkyl ether sulphate, at the same time as finely pore foams are obtained where desired, the invention entails a technical advance compared to GB-PS 952 356.

Claims (1)

Use of polyvinyl chloride produced by continuous polymerization in emulsion in the presence of water-soluble catalysts and 1.6 - 2.8 weight percent, calculated on the monomers, of an emulsifier system of a) 70-30 weight percent of an alkyl sulfate with the formula R - OS03Me, where R is an alkyl residue with 10 - 18 carbon atoms and Me is Na or K, b) 0-65 percent by weight of an alkyl ether sulfate with the formula R - (OCH2 - CH2)n - OS03Me, where n stands for a whole number from 1 to 5 and R and Me have the above meaning, and c) 0-60 percent by weight of a Na-alkylsulfonate whose alkyl chain carries 10-20 carbon atoms, with components a, b and c together making up 100% by weight, for the production of soft foams according to the coating method using chemical foaming agents.