CH662816A5 - METHOD FOR PRODUCING A CROSSLINKED PVC USE LAYER. - Google Patents

Description

The invention relates to the production of a crosslinked PVC wear layer according to the preamble of claim 1.

Polyvinyl chloride wear layers have found a wide variety of uses for wall and floor coverings. They are 5 mechanically resistant, flame retardant and have good chemical resistance. However, there are problems with the heat resistance of these thermoplastic layers. In particular, burning cigarettes leave undesirable permanent damage. In order to improve the heat resistance, the layers were cross-linked by electron beams and radioactive radiation or free radicals. The first two methods are costly and require extensive security measures; the third method delivers qualitatively unsatisfactory products. In order to avoid these disadvantages, it was proposed in FR-A 1 79 1983 to crosslink a film or plate formed from a mixture of polyvinyl chloride, a reactive plasticizer (crosslinking agent), a photosensitizer and a stabilizer by calendering by means of UV radiation . In order to avoid the inhomogeneity caused by the gelling of the reactive plasticizer due to the heat of calendering, a polymerization inhibitor is added to the PVC mixture. The calendered foils or plates are then glued or welded to a plate or other hard base under pressure before or after exposure to UV light. This method is therefore not suitable for the production of a wear layer for a soft and / or relief-like underlay, as is often used for floor coverings, since the latter give way when pressed together, which affects the quality of the connection or damages the relief.

It was therefore an object of the present invention to provide a method of the type mentioned at the outset which provides crosslinked, in particular heat-resistant PVC wear layers 35 for soft and sensitive substrates.

This object was achieved according to the invention by the features of the characterizing part of claim 1.

By applying a PVC preparation in a spreadable state to the base, the base material is mechanically stressed so slightly that e.g. existing relief structures are not affected. At the same time, there is continuous, continuous contact between the base and the PVC preparation, which, together with the subsequent gelling, results in an impeccable connection of the layers in contact. The spreadability also allows the relief structure of the base to be formed only after the PVC preparation has been applied, since the plastic PVC preparation does not hinder the deformation of the base.

50 The combination of the process steps according to the invention provides a PVC wear layer which is crosslinked by means of UV rays, heat-resistant, in particular resistant to burning cigarettes, and which remains soft, pliable and deformable -55 bar until crosslinked and can be handled without any problems during production can.

Surprisingly, it was found that due to the heat applied during the gelling, the cloudiness and unevenness of the PVC wear layer observed even at low temperatures without polymerisation inhibitor does not occur, so that a qualitatively perfect PVC wear layer leaves the gelling oven which is subsequently or at a later time subjected to crosslinking by means of UV radiation. 65 The use of the spreadable PVC preparation, i.e. the shape without heating allows a greater freedom of formulation than is possible with calendered sheets, e.g. the use of higher molecular weight PVC

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662 816

important and less crosslinking agent and the production of a softer product with up to 120 wt .-% of a commercially available plasticizer. In addition, there is a gelled, i.e. manipulable, but still thermoplastic wear layer, which allows the advantageous implementation of further steps between gelling and crosslinking. For example, the gelled PVC wear layer can be printed and / or sent for further processing.

Both semifinished products and removable intermediate supports can be used as a base for the method according to the invention. In the first case, the semi-finished product can contain a foamable layer, the foaming of this layer and the gelling of the PVC wear layer being able to take place in the same heat treatment. The semi-finished product provided with the gelled PVC wear layer or the intermediate carrier is subsequently or after further treatment steps are carried out for crosslinking. If necessary, the intermediate carrier can be removed from the gelled PVC wear layer before crosslinking.

Spreadable PVC preparations generally contain, apart from PVC, the known photosensitizers and crosslinking agents, which are preferably polyfunctional monomers and oligomers, plasticizers, thinners, heat stabilizers and catalysts or the UV stabilizers which counteract damage by UV radiation.

PVC types obtained by emulsion, suspension or microsuspension polymerization or mixtures thereof can be used for the process according to the invention. By choosing a polyvinyl chloride with a higher molecular weight, the degree of crosslinking and thus the heat resistance of the end product can be improved.

Commercial products, for example based on phthalate esters, can be used as plasticizers, as are usually used when mixing PVC plastisols. Since the type of this plasticizer also influences the degree of crosslinking of the end product, its selection can be optimized by preliminary tests. The PVC preparations can contain up to 120% by weight, preferably up to 80% by weight, of plasticizers without the heat resistance of the wear layer being impaired.

The thinners used are known and are already used for PVC plastisols. There are also reactive thinners, e.g. Monomers in question, which on the one hand can participate in the crosslinking reaction and on the other hand s control the reological processing properties of the mixture.

As heat stabilizers, those based on organic barium and zinc salts, e.g. Ba-Zu decanoates are used, as are already used for PVC plastisols.

Substances containing amine groups are particularly suitable as catalysts for the crosslinking reaction.

Reactive acrylic monomers and oligomers, the latter preferably having a molecular weight of 400 to 900, are preferably used as crosslinking agents. The use of oligomers with a higher molecular weight is possible, but requires special precautions when mixing. At least 20 trifunctional compounds are preferably used to achieve good heat resistance. The addition of monofunctional compounds improves the elasticity of the PVC wear layer. The strongest cross-linking and thus the best heat resistance is achieved with pentafunctional acrylics. In addition to their function as participants in the crosslinking reaction, the bifunctional acrylates also have those of reactive diluents.

To start the crosslinking reaction under the action of UV rays, free radical formers such as benzophenone, acetophenone and the like are used as photoinitiators. According to the invention, polymerization inhibitors, as are essential according to the known method for preventing the gelling of the polyfunctional monomers before UV irradiation, are not required.

In order to protect the PVC wear layer obtained against the destabilizing effect of UV rays, UV stabilizers can be used in the PVC preparation.

The invention is further illustrated by the following examples:

«Examples 1 to 7

PVC preparations were made with the following compositions:

Example No.

High molecular weight polyvinyl chloride

100

100

100

100

100

100

100

Dipentaerithritol monohydroxy pentaacrylate

9

9

9

9

9

-

-

(PENTA)

Trimethylolpropane triacrylate (TMPTA)

9

9

9

9

9

-

-

Benzophenone derivative as a sensitizer

0.7

0.7

0.7

0.7

0.7

0.7

0.7

Ba-Zn heat stabilizer

3rd

3rd

3rd

3rd

3rd

3rd

3rd

Dioctyl phthalate

60

-

-

-

-

60

60

Diisononyl phthalate

-

60

-

-

-

-

-

Benzyl butyl phthalate

-

-

60

-

-

-

-

Dinonyl adipate

-

-

-

60

-

-

-

Phosphoric acid esters

-

-

-

-

60

-

-

Trimethylalpropane trimethyl acrylate

-

-

-

-

-

35

-

Acrylic oligomer (MW = 900)

-

-

-

-

-

-

20th

Ethoxylated

Trimethylpropentrimethyl acrylate

25th

These preparations were applied to a siliconized release paper or an aluminum plate with a doctor knife, gelled in a hot air oven and crosslinked by means of UV radiation.

65 The individual samples show good resistance to heat when they are brought into contact with burning tobacco products.

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Examples 8 to 11

In these examples, the influence of the starting materials used on the degree of crosslinking and thus on the heat resistance is shown.

Determination of the degree of cross-linking

To determine the degree of crosslinking, the sample to be tested is extracted in a Soxhlet apparatus with tetrahydrofuran (THF) for at least 48 hours. The non-extracted residue is a measure of the degree of crosslinking, which is calculated as follows:

A) PVC + monomers maximum non-extractable fraction that can participate in the crosslinking

B) plasticizer

Share that is extracted and therefore does not participate in the networking

C) residue after extraction

Degree of crosslinking y = C 100%

A

Half of the sensitizer and heat stabilizer are divided into A and B.

Example 8

Influence of the polyfunctional monomer on the degree of crosslinking

a b

PVC

100

100

Benzyl butyl phthalate (BBP)

60

60

s heat stabilizer

4th

4th

Photoinitiator

4th

4th

Trimethylolpropane trimethyl acrylate

(TMPTMA)

50

-

Dipentaerithritol monohydroxypenta-10 acrylate - 50

Degree of networking 76.92% 99.27%

The use of a pentafunctional monomer (b) resulted in an end product which survived the extraction by tetrahydrofuran (THF) virtually unchanged.

Example 9

Influence of the plasticizer on the degree of crosslinking

20th

a b

PVC

100

100

TMPTMA

60

60

Heat stabilizer

4th

4th

Photoinitiator

4th

4th

Diisononyl phthalate (DINP)

60

-

Dioctyl phthalate (DOP)

-

60

Degree of networking

85%

89.4%

30th

The end products with DOP had a higher proportion of non-extractable material.

Example 10

35 Influence of the plasticizer content on the degree of crosslinking a b c d e f

Polyvinyl chloride

PENTA

TMPTA

Ba-Zn heat stabilizer UV sensitizer dinonyl adipate degree of crosslinking (%)

100

100

100

6

6

6

15

15

15

4th

4th

4th

1

1

1

50

60

70

66.9

66.1

66.2

100

100

100

6

6

6

15

15

15

4th

4th

4th

1

1

1

80

100

120

66.3

65

60.2

Increasing the plasticizer content from 60 to about 100 only slightly reduced the degree of crosslinking. A significant decrease can only be ascertained with a higher plasticizer concentration.

Example 11

Influence of the molecular weight of PVC on the degree of crosslinking

a b

PVC (K value: 63)

100

-

PVC (K value: 80)

-

100

TMPTMA

50

50

Heat stabilizer

4th

4th

Photoinitiator

2nd

2nd

BBP

60

60

Degree of networking 47.5% 65.8%

50

Higher molecular weight PVC resulted in a final product with a much higher proportion of cross-linked material.

Example 12

55 The following preparation has been prepared

PVC (K value = 100) 75

PVC (K value = 80) 125

60 pentaacrylate 20

Triacrylate 20

DOP 120

Heat stabilizer 6

Photoinitiator 2

65 UV stabilizer 0.2

With the coating technique, she was able to apply it to a surface without any problems. Your storage stability was good.

Example 13

The preparation according to Example 12 was mixed, filtered and deaerated by a process customary for the production of plastisols and processed in a system known per se and shown schematically in FIG. 1.

In this system 1, a semi-finished product 3 is drawn off from a supply roll 2 and carried out under a doctor knife 4, with which the plastisol according to Example 12 is applied. In a subsequent hot-air oven 5, a layer of a semi-finished product 3 containing a blowing agent is foamed by the action of heat and the plastisol is gelled, its thermoplastic properties being fully retained. The latter are essential for the subsequent processing steps. The semifinished product passes through the hot air oven 5 with a temperature profile of 190-205-210-190 ° C at a speed of 15 m / min, which results in a dwell time of about 2 min 30 s.

Then the semi-finished product, with the foamed layer and the gelled wear layer, is swept in the station 6, and a back coating is applied with a coating device 7. The latter is gelled in an oven 8. The web emerging from the furnace 8 for crosslinking the PVC wear layer is then carried out under high-pressure mercury lamps 9 with an output of 80 and 120 W / cm. These UV lamps have a selective emission spectrum from 250 to 420 nm. The web-shaped product 11 obtained is then either fed to a supply roll 12 and wound up or packaged directly into finished products in rolls of lengths customary in the industry.

This product 11, which can be used as a floor covering, has the structure shown schematically in section in FIG. 2.

The back coating 13, which has a cellular structure, was applied with the coating device 7 and is to be placed on a support, e.g. Soil, determined. The back coating is followed at the top by a carrier 14 which was already contained in the semi-finished product 3 and which guarantees the dimensional stability of the product 11. A foamed layer 15 with a relief structure and a print pattern 16 is arranged on the carrier 14. This layer 15 was foamed in the oven 8 simultaneously with the gelling of the transparent wear layer 17, the relief structure also being achieved.

The manufacture of the semi-finished product 3 or the foaming into a layer with a relief surface is described in detail in Swiss Patent 458,712. The PVC wear layer 17 of the product obtained is homogeneous, transparent and shows no permanent changes in its contact with burning tobacco products or in the expression of burning cigarettes on its surface. It is up to about 350 ° C 662 816

resistant. On the other hand, with conventional wear layers, irreversible damage to the wear layer and, as a consequence, to the foamed layer underneath, can be observed even at much lower temperatures.

The heat resistance was tested with a stamp under a pressure of 1 bar (0.1 N / mm2) with increasing temperature. A common PVC wear layer of about 0.5 mm thickness was completely penetrated at 130 °. In contrast, only a penetration depth of about 67% was observed for a PVC wear layer according to Example 12, also 0.5 mm thick at 340 °, i.e. the layer below the wear layer was not injured.

On the surface of the gelled wear layer, preferably immediately before crosslinking, a very thin lacquer layer made of UV-crosslinkable material can be applied and crosslinked together with the wear layer. The use of such plasticizer-free lacquer layers based on acylate as dirt-repellent layers is already known from US Pat. No. 4,100,318. In the present case, they additionally allow easier removal of scorch marks from cigarettes.

While in US Pat. No. 4,100,318 the lacquer layer is only mechanically connected to the underlying layer made of normal soft PVC, the advantage of the embodiment according to the invention is that crosslinking takes place across the layers and thus an optimal anchoring of the lacquer layer is guaranteed.

In addition to the floor covering described above in detail, wall coverings, coverings, self-supporting wear layers and so-called homogeneous coverings can be produced according to the invention. In the latter case, the gelled PVC wear layer is applied to the calendering coverings by an intermediate support and then crosslinked.

In order to make the process as economical as possible by using smaller amounts of acrylate crosslinking agent, the wear layer can be applied to the base in two steps, the PVC preparation applied in the first step containing no crosslinking agent. This first wear layer part can then be gelled before the second wear layer part containing the crosslinking agent is applied. Furthermore, the wear layer can be networked in two steps according to the invention. The first partial crosslinking step is carried out as close as possible after the gelling oven and the second step at the end, as in one-step crosslinking. After partial crosslinking, the wear layer still remains soft and flexible, i.e. the properties which are favorable for handling are retained, however, they have a higher lubricity and require less care in handling.

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5

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1 sheet of drawings

Claims (17)

662 816 1. A process for producing a UV-crosslinked, in particular heat-resistant, polyvinyl chloride wear layer from a preparation comprising a polyvinyl chloride, a crosslinking agent and a photosensitizer, characterized in that the preparation is spreadable on a base, in a first step The effect of heat gels and in a further step cross-linked by UV radiation. 2. The method according to claim 1, characterized in that the spreadable preparation is applied to the base in the form of a plastisol. 2nd PATENT CLAIMS 3. The method according to claim 1 or 2, characterized in that the spreadable preparation is applied to a foamable layer, the foamable layer is foamed in the first step by heat treatment and the preparation gels and in a further step the polyvinyl chloride wear layer is UV-coated. Radiation cross-linked. 4. The method according to claim 3, characterized in that after the gelling of the polyvinyl chloride wear layer on the side facing away from the sheet obtained, another layer is applied, this is gelled and then the polyvinyl chloride wear layer is crosslinked by means of UV rays. 5. The method according to claim 1 or 2, characterized in that the spreadable preparation is applied to a removable carrier. 6. The method according to claim 5, characterized in that the polyvinyl chloride layer is removed from the support after gelling, laminated onto a fabric and then crosslinked by means of UV radiation. 7. The method according to claim 6, characterized in that a flexible semi-finished product ver. turns. 8. The method according to claim 6, characterized in that composite sheets are used as the flat structure. 9. The method according to claim 6, characterized in that one uses a thermoplastic fabric. 10. The method according to any one of the preceding claims, characterized in that a polyfunctional monomer and / or oligomer and optionally a monofunctional monomer is used as the crosslinking agent. 11. The method according to any one of the preceding claims, characterized in that a 3- to 5-functional acrylate is used as the crosslinking agent. 12. The method according to any one of the preceding claims, characterized in that one does not use a polymerization inhibitor in the preparation. 13. The method according to any one of the preceding claims, characterized in that a preparation containing up to 100 parts, preferably 80 parts, of a plasticizer, based on 100 parts of polyvinyl chloride, is used. 14. The method according to any one of the preceding claims, characterized in that a lacquer layer consisting essentially of the crosslinking agent, preferably made of acrylate, is applied to the gelled polyvinyl chloride wear layer and the latter is crosslinked together with the wear layer by means of UV radiation. 15. The method according to any one of the preceding claims, characterized in that crosslinking in several, preferably two, steps by means of UV radiation. 16. Wear layer, produced by the method according to one of claims 1 to 15. 17. Floor or wall covering with a wear layer according to claim 16.