DE1900413A1 - Process for the production of cross-linked, thermoplastic foam plastic sheets - Google Patents

Description

CHEMICAL WORKS HÜLS AO 4370 Mari, 3.I.I969

- Patent Department - 2066 / J

Our reference: O.Z. 2355

Process for the production of cross-linked, thermoplastic foam plastic sheets

The invention relates to the production of crosslinked, thermoplastic foam plastic webs by heating a preformed, expandable, crosslinkable, thermoplastic material under increased pressure and subsequent relaxation.

The production of foamed plastic webs from thermoplastics is known in principle. - So can such Moldings produced by extruding expandable mixtures or by brushing or pouring on expandable, pasty or liquid, thermoplastic mixtures obtained on endless substrates and subsequent foaming by heating , whereby the shaping is carried out in a warm plastic state.

There has been no lack of attempts to convert crosslinkable thermoplastics into foamed plastic webs in a continuous way at elevated temperatures. Crosslinkable thermoplastics are understood below to mean homopolymers, copolymers or polymer mixtures which have been converted into a crosslinkable state by post-treatment or by copolymerization . The flow behavior of such expandable, crosslinkable thermoplastics, which contain the crosslinking agents blended or also optionally polymerized;

1 drawing

009833/1833

- 2 -. OZ 2335

3.1.1969

is changed by the presence of the crosslinking agents in such a way that that the mechanical movement of the mass at the necessary "processing temperatures is not possible because the occurring Friction does not allow the production of a cross-linked foam plastic. In particular, such difficulties arise when foaming crosslinkable polyolefins. There is therefore the task of such thermoplastics in the processing area to maintain the low flow viscosity, but to lower the flowability. If this does not succeed, the gas phase still has the possibility of freeing itself from the polymer during cooling, since the foam is not yet sufficiently solidified and thus coincides.

There are a wide variety of devices, such as calenders and rolling mills, known, but due to the existing friction, they are not suitable for the production of crosslinked, thermoplastic Plastic sheets are suitable.

For example, it is known from French patent specification 1 218 022 to vulcanize and relax a mixture to be carried out at the same time, in that individual forms are continuously guided over an endless belt, with the pressure within the shape is changed in the course of wandering with. Crosslinked thermoplastic foam plastics are therefore still produced discontinuously in compression molds, since it did not succeed in the continuous operation To prevent friction.

It has now been found that crosslinked, thermoplastic foamed plastic webs can be produced by heating a preformed, expandable, crosslinkable thermoplastic by heating under increased pressure and then relaxing «

009833 / 183.3 OR.ginally inspected

- 3 - OZ 2355

3.I.I969

can provide if you the preformed, expandable, crosslinkable, thermoplastic material continuously in a pressure-resistant, heated form, through which the mass without the action of Priktionskruppen according to its rate of addition conveyed further and, after emerging from the mold, is foamed by relaxing.

An expedient device for carrying out the method consists in a device which is mounted so as to be rotatable about a horizontal axis Use a heatable drum (1) over which a feed device for the preformed, expandable thermoplastic (2) is provided, through which the plastic mass on the drum shell (3) is applied. The drum surface contains a groove (5) across the width of the plastic web. This groove (5) is connected to a pressure belt (4), which moves in the direction of rotation of the drum, pressure-tight and tightly closed.

Suitable thermoplastic, crosslinkable, expandable plastic materials are, for example, mixtures of plasticizer-containing polyvinyl chloride (plasticizer content of 20 to 80 percent by weight) and synthetic rubber, in particular rubber-like butadiene-acrylonitrile copolymers, which vulcanizing agents and expanding agents, which are released in the heat above 100 ° C decompose of nitrogen, contain; Further, as containing polyolefins polyethylene polypropylene, polybutylene, the peroxides and blowing agents which decompose above 120 ⁰ C under liberation of nitrogen, where the peroxides are used to Vernetzbarmachen of polyolefins.

The following are used as crosslinking agents: thiuram compounds, e.g. tetramethylthiuram disulfide, sulfenamides, e.g. benzothiazyl-2-cyclohexyl-bulfenamide, or sulfur.

009833/1833

ORIGINAL INSPECTED

- 4 - 0.2, 2355

3>. I. 1969

Suitable nitrogen-releasing blowing agents are those with a decomposition point above ICK) ⁰ Cj, for example azodicarbonamide, diphenylsulfone - ^^ - disulfohydrazide and azoisobutyric acid dinitrile. They are used in amounts from 0.1 to 10 percent by weight, in particular from 1 to 1 percent by weight.

Peroxides are used to make polyolefins crosslinkable * which decompose above 160 ° C. weight percentage, used.

In this case, cobalt octoate is used as the crosslinking agent, 2,5-dimethylhexane-2,5-dihydroperoxide.

The process is carried out at temperatures above 100 ° C to obtain, applies when using cross-linkable polyvinyl temperatures above 16o ° C, in particular those of I6ö to 200 ⁰ C.

When producing cross-linked polyolefin foam sheets

By
from 180 to 250 ⁰ C.

one uses temperatures above IQO ⁰ C, in particular such

The crosslinkable, expandable, friction-sensitive thermoplastics are on machines that are kept so cold that the blowing agent and the crosslinking agent do not yet react, preformed to sheets, skins, strands. These preformed plastic sheets become the movable, tight-locking form continuously fed.

The process should be explained in more detail with the aid of the drawing:

The preformed, expandable, crosslinkable, thermoplastic plastic web (2) is continuously fed through the feed device

0 9 8 3 3/1833 ORIGINAL INSPECTED

- 5 - OZ 2355

3.1.1969

The device is fed into the gap formed by the heatable drum (1) and the printing belt (4). As it rotates around the drum, the propellant is decomposed and the crosslinking agent reacts. The accompanying pressure band (4) prevents premature expansion due to its gas-tight seal. When the pressure band (4) runs off in a predetermined manner, the warm plastic material continuously emerges from the mold and is foamed by relaxing it. The groove (5) and the pressure band (4) can be structured or smooth, so that the plastic web can be given a structured surface, if desired. The running plastic web (6) can be cut to length in the usual way using cross cutters. The method can be used for the customary production of foam plastic sheets, such as mattresses or also foils. Depending on the desired thickness of the foam plastic sheet, the depth of the groove (5) is kept larger or smaller. The groove (5) is designed by inclined side walls; It is advisable to provide a design as shown in Figure 2 in order to achieve a tight closure with the pressure band (4).

example 1

A heatable steel drum with a diameter of 3 m is heated to 180 ° C. The drum contains a groove 8 mm deep, which extends over 90 % of the width of the drum. 3/4 of the groove depth is covered with a pressure band. The synchronously running drum and the printing belt have a speed of 1.4 m / min. This corresponds to a residence time for the crosslinkable plastic material of 5 minutes. The device is a preformed Miaohung, consisting of

ORIGINAL INSPECTED

- 6 - OZ 2355

3.1.1969

80 parts by weight of polyvinyl chloride (Κ value 70) 35 parts by weight of plasticizer (dibutyl phthalate or

Benzyl butyl phthalate)

35 parts by weight of rubbery butadiene acrylonitrile

Copolymer (BUNAN)

5 parts by weight of Azodlcarbonamld 25 parts by weight of fillers

2 parts by weight of sulfur and 0.5 part by weight of benzothiazyl-2-cyclohexyl-sulfenaniide

fed. During the orbital period in the moving form becomes the propellant decomposes and the mass crosslinks. When it leaves the rotating mold, the plastic compound expands »and it a networked foam plastic sheet is created.

Example 2 On an extruder, a mixture is produced at around HO ^{0 C}

100 parts by weight of polyethylene 4 weight points azodicarbonamide 2 parts by weight of cobalt octoate in solution 1:10 and 2 parts by weight of 2,5-dimethylhexane-2,5-dihydroperoxide

produced, whereby a crosslinking and a decomposition of the propellant does not yet take place, the mass, which has been preformed into a film, is fed to the heatable drum and the printing belt via a slot die. The temperature of the drum is 200 ^° C. Under otherwise identical conditions, the mass with the rotating mold is passed over the drum and, after leaving the printing forme formed from drum and printing belt, foams continuously to form a foam sheet.

009833/1833

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3.I.I969

Example 3

The following mixture is processed under the conditions of Example 1:

70 parts by weight of polyvinyl chloride (K value 70) 30 parts by weight of elastomeric butadiene acrylonitrile

Copolymer

30 parts by weight of phenol alkyl sulfonic acid esters

and cresols

2 parts by weight of stabilizer (Ba-Cd-Zn complex)

1 part by weight of stearic acid

20 weight point chalk

5 parts by weight of titanium oxide

5 parts by weight of zinc oxide

1 part by weight. sulfur

0.3 part by weight of benzothiazyl-2-cyclohexyl-sulfenamide

0.1 part by weight of tetramethylthiuram disulfide

10 weight points diphenyl sulfone «-3 # 3-disulfohydrazide

A cross-linked foam plastic sheet is obtained.

0 0 9 8 3 3/1833 ^{0 RIGINAL INSPECTE} &

Claims (2)

190041 - 8 - O.ζ. 2355 5.1.1969 claims 1. A method for producing crosslinked, thermoplastic foam plastic webs by heating an expandable, crosslinkable, thermoplastic material under increased pressure and subsequent relaxation, through this . characterized in that the preformed expandable, crosslinkable, thermoplastic Plastic mass is continuously given into a pressure-resistant, heated mold, through which the mass without the action of Frictional forces are further conveyed according to their rate of addition and after exiting the mold by relaxing is foamed. 2. The method according to claim 1, characterized in that it is used as a crosslinkable, expandable, thermoplastic synthetic material crosslinkable polyethylene or mixtures of polyvinyl chloride and elastomeric butadiene-acrylonitrile copolymers are used. 3 · Device for carrying out the method according to the claims 1 and 2, in which a feed device is provided over a heated drum (1) rotatably mounted about a horizontal axis is provided, through which the crosslinkable, expandable, thermoplastic synthetic material is applied to the drum shell (3) will, characterized in that the drum surface corresponds to the width of the plastic web Groove (5) and this groove with a moving according to the direction of rotation of the drum with the drum speed Pressure band (4) is firmly connected. 009833/1833 ORIGINAL INSPECTED