CA1084355A

CA1084355A - Base material for artificial leather

Info

Publication number: CA1084355A
Application number: CA243,994A
Authority: CA
Inventors: Gustav Sinn; Martin Matner; Hermann J. Bross
Original assignee: Bayer AG
Current assignee: Bayer AG
Priority date: 1975-01-23
Filing date: 1976-01-21
Publication date: 1980-08-26
Also published as: SE7600654L; NL7600551A; BG26540A3; IT1053402B; AR214970A1; CS186235B2; GB1534762A; DD125768A5; PL107608B1; GB1534763A; CH605121A5; FR2298433B1; HU177543B; JPS5195103A; RO70418A; BR7600378A; FR2298433A1

Abstract

A BASE MATERIAL FOR ARTIFICIAL LEATHER
ABSTRACT OF THE DISCLOSURE

A base material for artificial leather having a water vapour absorption capacity of from 2 to 8% by weight, based on a fibre fleece impregnated with a rubber latex mixture containing a heat sensitizer, a quick-acting vulcanisation accelerator and, as expanding agent, a silicone oil emulsion or an inert, emulsifiable substance which is insoluble both in the rubber and the other constituents of the latex.
After the impregnation of the fibre fleece, the latex mixture is coagulated by heat, vulcanised and then dried.

Description

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This invention relates to a ba~e material for arti~icial leather based on fibre fleeces impregnated with a rubber lntex~ and to a proce~s for the production of this base material The base material for artificial leather 5 according to tha invention has a particularly high water vapour abs ~ ~on capacity which reaches about 70 ~ to 80 ~ of the ab~or~on capacity of natural leather.
Microporous sheet-form materials permeable to water vapour and based on substrates impregnated with rubber latices are known from DT-AS 1,570,088. Although these products are microporous and, hence, show a certain permeability to water vapour~ they have no absorption capacity for water vapour. The process by which they are produced is unsuitable in practice for the production o~
large surfaces on a commercial scale because the latex mixtures used are only stable for a ~hort period and~
hence, are unsuitable for continuous impregnating processes.
Accordingly, there is a need tv provide a base material for artificial leather which, on the one hand, has a high water vapour absorption capacity and which, on the other hand, can be manufactured easily and reproducibly. The water vapour ab~orption capacity isparticularly important because it is one of the most outstanding propertie~ of natural leather and~ hitherto~ it has never been adequately reproduced ln synthetic product~
Accordingly~ the present invention provides ~ ba~e materlal for arti~icial leather ba~ed on a ~ibre fleeoe 1mpregna'ced with a rubber latex~ which is characterised by a water vapour ab~orption capacity o~ from 2 to 8 Le A 16 246 - 2 -.

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by weight, based on the dry weight oF the ~aterial, a tensile strength of from 30 to 250 ~g/cm and an elongation at break of from 30 to 150 %.
The process for producing this base material for artificial leather by impregnating a fibre fleece with a rubber mixture, coagulating the mixture, followed by vulcanisation, is distinguished by the fact that a fibre fleece is impregnated with a rubber latex mixtu:re containing a heat sensitiser, a - quick-acting vulcanisation accelerator and, as expanding agent, a silicone oil emulsion or an inert, emulsifiable substance which is insoluble both in the rubber and in the other constituents o~ the latex and, after coagulation of the latex mixture by heating it, is vulcanised, preferably in steam, and then dried. More particularly, the fibre fleece is impregnated with a rubber latex mixture which is used in an amount of from 50 to 200 % by weight of said fleece; said rubber latex mixture containing 100 to 300 parts by weight of water, 100 parts by weight of rubber, 0.5 ~o 5 parts by weight of a heat sensitiser, 3 to 10 parts by weight of a vulcanisation agent, 1 to 4 parts by weight of a quick-acting vulcanisation accelerator and 0.5 to 10 parts by weight of an expanding agent.
Fibre fleeces suitable for the production of the artificial leather base material are, in particular, fleeces consisting of natural and/or ~ -synthetic fibres. Polyamide, polyester, polypropylene, viscose and cellulose fibres are preferably used.
Rubber latices suitable for impregnation are, in principle, any heat-sensitisable natural or synthetic rubber latices. Particularly suit-able rubber latices are natural rubber latex and synthetic rubber latices such as, for example carboxylated and non-carboxylated latices based on copolymers of butadiene/acrylonitrile, butadiene/styrene, chloroprene and butadiene/acrylic acid esters, and also isoprene and corresponding copo-lymers. In addi*ion, the polymers may contain acid amide functions and autocrosslinking groups such as, for example, N-methylol acrylamide.
Heat sensitisers which may be used in accordance with the inven-- tion are, for example, polyvinyl methyl ethers, polyethylene- and poly-propylene oxide adducts and/or ~ 3 ~
.~

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.. their co-ad~ucts9 polyalkyl and poly~ryl siloxanes and ethylene ~- diamine polyether adducts.
Vulcanisation agents are, for example, dispersion mixture~
consisting of sulphur, zinc oxide and ~ulcanisation accelerators In the case of reactive polymers which normally crosslink in the absence of sulphur and vulcanisation accelerators~ suitable crosslinking agents are condensation products of melamine~
urea or phenol with formaldehyde, or metal oxides.
It is preferred, however, to use polymers which contain no autocrosslinking groups. For the crosslinking o~ these polymers according to the present invention the latex is compounded with a mixture suitable for vulcanisation, preferably in form of a dispersion or a paste. This paste contains in addition to water, a dispersing agent, and known ~illers like titanium dioxide the usual vulcanising agents like sulfur and ¦ zinc oxide and according to the invention a quick-acting water-soluble vulcanisation accelerator besides a water-insoluble vulcanisation accelerator.
The presence o~ a quick-acting vulcanisation acceler~tor is of particular importance. Suitable quick-acting vulcanisation accelera~ors are, primarily, water-soluble - sodium or ammonium salts of variou~ derivatives o~ dithio--` carbamic acid, optionally in combination with salts of , ~
~-- merc~ptobenzothiazole.
Quick-acting water-soluble vulcanisation accelerators are for example the alkaline metal, alkaline earth metal9 a~d ; ammonium salts o~ dimeth~l, diethyl, diisopropyl and dibutyl ' dithiocarbamic acid.
Water-insoluble vulcanisation accelerators are ~or example ~ 30 the zinc salts of the above-mentioned dithiocarbamic acids 9 ; Le A 16 246 - 4 -.
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~8~3~5 mercaptobenzothlazole and it~ zinc salt~, thiurame and its derivatives.
.. A suitable dispersing agent is for example the conden-sation product of naphthalene sul~onic acid and formaldehydeO
The vulcanisation paste according to the present invention is composed as follows:
C.5 to 10.0 parts by weight of zinc oxide, pre~erably about 5.0 parts by weight . O.2 to 10.0 " " sulfur, pre~erably about

2.0 parts by weight 0 2 to 3.0 " " of water-soluble accelerator, ;- pre~erably about 1.0 parts by weight '?` 0.2 to 3.0 " " of a water-insoluble accelerator, preferably about 1.0 part~ by weight 2.0 to 15.0 " " titanium dioxide, preferably about $.0 parts by weight i 0.1 to 7.0 " " a dispersing agent, preferably about 1.0 part8 by weight 10.0 to 50.0 " " water, prPferably about 25.0 parts by weight.
- The amount of vulcanisation paste to be applied may vary over a wide range Usually 10 to 100 parts by weight, pre~er-ably 30 to ~0 parts by weight, and most preferably 40 parts by weight of the vulcani~ation pa~te are applied on 100 parts ~- 25 by weight of rubber (based on the weight o~ dry substance) The vulcanisation paste is prepared by adding the rest of the components to the water and the disperqing agent or to -~ an according solution o~ the di~persing agent in water, re~pectively. The mixture and itQ ingredients are then inten-sively mixed and triturated for 12 to 72 hours, pre~erably ~or ~ Le A 16 246 - 5 -:' :: :

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24 hours, for example in a roller mill. In this way a vul-canisation paste is obtained which is ready ~or use and contains its ingredients in a finely divided ~orm.
Insoluble and inert subætances ~uitable for use as expanding agents in accordance with the invention are:
l) long-chain aliphatic or alicycllc isocyanates, 2) condensates of N-methylolated melamine, urea or cyelic :; ureas with long-chain fatty acids or their amides, long chain ~lcohols and long-chain amines9 c 10 3) per~luorinated long-chain aliphatic compounds~

4) polyvinyl methyl ethers,

5) mixtures o~ epoxide resins with polyether siloxane~
. 6) mixtures of polyethylene with polyether siloxane9 7) mixtures of the products mentioned in l) to 6).
Examples of products of this kind are stearyl isocyanate;
~-~ the condensate of hexamethylolated melamine with behenic acid; per~luorinated stearic acid; polyvinyl methyl ether~ -. having a molecular weight in the range o~ ~rom 30,000 to $. 709000 and mixtures of low molecular weight polyethylene with polyether siloxane Silicone oils which are particularly suitable for use as exp~nding agents are silicone oil9 having a vi~eoæity o~ from 50 to lO00 cP which are used in the form of aqueou~ emul~io~
- having a solid~ content of~ pre~erably~ from lO to 50 ~ and which preferably co~tain non-ionic emulqi~ier~, I~ ge~eral, the rubber latex mixture contains from lO0 to 300 part~ by weight9 pre~erably about 220 parts by weight~ of water; lO0 part~ by weight of rubber; from 0.5 to 5 parts by weight, preferably about l.0 part by weight, of heat sensiti~er; irom 3 to lO parts by weight~ preferably

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about 7.0 parts by weight, of vulcanisation agent; from 1 to 4 parts by weight, pre~erably about 2 0 parts by wei~ht o~
vulcanisation accelerator; and ~rom 005 to lO parts by weight, prefera~ly about 5.0 parts by weight, of ex~anding agent.
The fibre fleece is impregnated with this mixture in the usual way, a quantity of ~rom 50 to 2V0 ~ based on the fibres, generally being used.
The fleece thus obtained is then heated to a temperature of ~rom 25 to 80C. Since the latex mixture contains a heat sensitiser, it is stable below this temperature, but coagulates very quickly above a predetermined critical temperature After coagulation, the impregnated fibre fleece has to be immediately vulcanised It is important to carry out vulcanisation as quickly as possible. For this reason~
vulcanisation is preferably carried out with steam at temperatures in the range ~rom 100 to 200C Vulcanisation generally lasts ~rom 5 to 60 minutes. The vulcanised, - impregnated fibre fleece may then be dried in ~he usual way, for example in vacuo, at 100 to 170C.
!, An artificial leather base material whose outstanding property is its water vapour absorption capacity is obtained in this way~ It may be provided with a surface layer in known manner~ for ex~mple by applying a thin microporous polyurethane - layer. I$ may then be fini3hed~ again in the usual way~ to give a particularly highquali$y arti~icial leather who~e ~- properties 3ubstantially correspond to those of natural ,. ~
leather.
~- E~AMPLE 1 A needle-punched and subseque~tly shrunk random fibre fleece~
consisting of 60% by weight of polyamide fibres (approximately Le A 16 246 - 7 -,''.'' ,. . .

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40 mm staple length and 1.5 den) and 40% by weight of poly ester fibres (approximately 40 mm staple length, 1.5 den), is impregnated with an excess of a latex mixture having the compo-` sition specified below, so 1;hat 100 g of solids are taken up f 5 from the latex mixture per 100 g of fibre material. The impreg-nated fleece is then quickly heated to 50C, as a result of which the latex mixture gels. A~ter vulcanisation with steam for 30 minutes at 105C, the fleece is dried in hot air. The fleece is then split so that the end product has the layer thickness indicated in T~ble 1. A microporous base material ~- for artificial leather is obtained. The ~leece has a water vapour absorption capacity o~ 4.4 % (as determined by the method described below).
~ The latex mixture used has the following compositlon:
t 15 210.0 parts by weight of a 47 ~ latex of a copolymer o~ 85 ~0 by weight of butadiene and 15 % by weight o~ acrylo-nitrile (= 100 parts by weight of dry substance) 10.0 part~ by weight of a 50 ~ by welght silicone oil emulsion (100 - 1000 cP) in a 2% aqueous solution o~
the condensation product of 1 mol o~ benzyl phenyl phenol and 20 mols o~ ethylene oxide~
1.0 part by weight o~ a polyether siloxane, 8.0 parts by weight oi benzyl phenyl phenol, 75.0 part~ by weight of water, - 25 41.0 parts by weight of a vulcani~ation paste of 2 part~ by weight of colloidal 3ulphur, 5 parts by weight oi zinc oxide, 1 part by weight o~ zinc diethyl dithio-carbamate, 5 parts by weight of titanium dioxide, 1 part by weight Or sodium diisopropyl dithiocarbamate and 27 parts by weight o~ ~ 5 % aqueous solution of a condenea-Le A 16 246 - 8 -, ;: :

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tion product of naphthalene sulphonic acid with formal-dehyde.
The coagulation point of thi~i latex mixture is approximately 40C.
Comparison Test 1 This test is carried out in exactly the same way, except that neither the silicone oil emulsion nor the sodium diisopropyl dithiocarbamate ~very quick Accelerator) is added. In addition, vulcanisation is carried out in hot air at a temperature of from llO to 130C and not in a steam atmosphere. The ~ material thus obtained has a water ~apour absorption ! capacity of o.6 ~.
The results are summarised in Table 1, The corresponding values ~or skiver are also shown for comparison.
EXAMPLES 2 to 4 ' A random fibre fleece consisting of 60% by weight o~ poly-amide flbres (approximately 40 mm staple length, 1.5 den) and 40% by weight of polyester fibres ~approximately 40 mm staple .- 20 length, 1.5 den), is impregnated with an excess of a latex mixtura having the composition specified below, so that 100 g o~
t~ solids are taken up from the latex mi~ture per 100 g o~
~ibre material. The impregnated fleece is then quickly `~ heated to 50C) as a result of which the latex mixture gels.
-~ 25 A~ter vulc~ni~ation with ~team for 30 minutes at 105C~
the fleece is dried in hot air. The fleece is then split so that the end product has the layer thickness indicated r" ~ in Table 2, A microporous base material for artificial i .-leather is obtained. The ~leeces have a water vapour absorpt~n capacity of from 4 to 5 ~ (as determined by the ~ Le A 16 246 - 9 -., -. ~ ~ . - -.

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metho~ described below; cf. Table 3~.
The latex mixture used hlas the following composition:
210.0 pnrts by weight of a 47 ~0 latex of a copol~ner of 60.0 %
by weight of butadiene and 36 ~ by weight of acrylonitrile and 4.0 ~ by ~eight of methacrylic acid (= 100 parts by r weight of dry substance)g a) 15 parts by weight o~ stearyl isocyanate, 33 ~S
: emulsion, or b) 15 parts by weight of a mixture of polyeth~r siloxane with polyethylene) 33 $ emulsion, or c) 30 parts by weight of the condensation product of ` methylolated melamine with behenic acid, 16.5 %
.- emulsion, or - d) 30 parts by weight of polyvinyl methyl ether, molecular weight approximately 50,000~ 16.5 %
. emulsion~
; 1.0 part by weight o~ a polyether siloxane, 2.0 parts by weight oi benzyl phenyl phenol, ~ 75.0 parts by weight of water, t 20 41.0 parts by weight of a vulcanisation paste of } 2 parts by weight of colloidal sulphur, 5 parts by ~ weight of zinc oxide, 1 part by weight o~ zinc diethyl r dithiocar~amate7 5 parts by weight of titanium dioxide~ :
1 part by weight of sodium diisopropyl dithiocarbamate and 27 parts by weight of a 5 % solution of a condensatio~
~"
product of naphthalene sulphonic acid with ~ormaldehyde.
~- The coagulation point of this latex mixture is approximately 40Co ComPjarison Test 2 ~his test is carried out in exactly the same way~ except Le A 16 246 - 10 -.'`.';' .
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that neither the inert substances which are insoluble both in the rubber and in the other constituents of the latex nor the sodium diisopropyl dithiocarbamate (very quick accelerator) are added. In addition, vulcanisation is not carried out in a steam atmosphere, but in hot air at a temperature in the range of ~rom 100 to 130C. The material thus obtained has a water vapour absorption capacity of 0.6%.
The results are summarised in Table 2 and 3. The corresponding values for skiver are also shown for comparison ''~ ' .
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Water vaPour ~
. after 4 a~ter 8 after 24 hours ~ hours ~ hours %
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Comparison test o.6 o.6 o,6 Skiver 5.3 6,2 6.9 Example a) 1.4 2,1 3.9 Example b) 1.7 2.2 4.4 Example c) 1.5 2.7 4.4 Examplc d) 1.7 2,2 4.8 *) by the method described below The water vapour absorption capacity was d~termi~d - as ~ollows:
The test specimens (mea~uring 50 x 20 mm) were prepared for 24 hours at 20C in a conditioned room with a relative air humidity of 65 ~. Thereafter they were accurately weighed (to 0.0001 g) and then introduced into a conditioned room with a relative air humidity of 86 ~ at 20C, After storage for 4, 8 and 24 hours, they were reweighed and the increase in weight determined to an accuracy of 0.0001 g~
The result of measurement is the percentage increase in weight based on the weight obtained after conditioningO
The results quoted are a~erages of three individual results.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A base material for artificial leather based on a fibre fleece impregnated with a rubber latex, characterised by a water vapour absorption capacity of from 2 to 8% by weight, based on the dry weight of the material, a tensile strength of from 30 to 250 kg/cm2 and an elongation at break of from 30 to 150%.

2. A process for producing the base material for artificial leather claimed in claim 1 by impregnating a fibre fleece with a rubber mixture, coagulating the mixture, followed by vulcanisation, wherein a fibre fleece is impregnated with a rubber latex mixture, said rubber latex mixture being used in an amount of from 50 to 200 % by weight based on the weight of said fleece, said rubber latex mixture containing 100 to 300 parts by weight of water, 100 parts by weight of rubber, 0.5 to 5 parts by weight of a heat sensitiser, 3 to 10 parts by weight of a vulcanisation agent, 1 to 4 parts by weight of a quick acting vulcanisation accelerator and 0.5 to 10 parts by weight of an expanding agent, said expanding agent being an inert, emulsifiable substance which is insoluble both in the rubber and in the other constituents of the latex and, after coagulation of the latex mixture under heat, is vulcanised and then dried.

3. A process for producing the base material for artificial leather claimed in claim 1 by impregnating a fibre fleece with a rubber mixture, co-agulating the mixture, followed by vulcanisation, wherein a fibre fleece is impregnated with a rubber latex mixture, said rubber latex mixture being used in an amount of from 50 to 200 % by weight based on the weight of said fleece, said rubber latex mixture containing 100 to 300 parts by weight of water, 100 parts by weight of rubber, 0.5 to 5 parts by weight of a heat sensitiser, 3 to 10 parts by weight of a vulcanisation agent, 1 to 4 parts by weight of a quick acting vulcanisation accelerator and 0.5 to 10 parts by weight of an expanding agent, said expanding agent being a silicone oil emulsion and, after coagulation of the latex mixture under heat, is vulcanised and then dried.

4. A process as claimed in claim 2, wherein vulcanisation is carried out in a steam atmosphere.