CA1165083A

CA1165083A - Molded article of a synthetic resin with a peroxidically crosslinkable component and process for the manufacture thereof

Info

Publication number: CA1165083A
Application number: CA000371941A
Authority: CA
Inventors: Karl-Heinz Spiess
Original assignee: Dynamit Nobel AG
Current assignee: Dynamit Nobel AG
Priority date: 1980-02-28
Filing date: 1981-02-27
Publication date: 1984-04-10
Also published as: DE3007531A1; JPS56143225A; EP0035117A2; EP0035117A3

Abstract

ABSTRACT OF THE DISCLOSURE:
The present invention relates to a molded article made of a resin molding composition containing at least one peroxidically crosslinkable component, characterized in that said peroxidically crosslinkable component is present in the molded article in a homogeneous distribution and in that the peroxidically crosslinkable component, in part of the molded article which includes at least part of the surface of the molded article is crosslinked by means of a peroxide; the present invention also provides a process for making the above defined molded article. The molded articles according to the present invention enjoy physical properties common to crosslinked resins while retaining weldability.

Description

0 ~ 3 qlhe invention relates to a molded article made o~ a resin (e.g. synthetic) molding composition containing at least one peroxidically crosslinkable component and optionally, if desired a filler and/or other additive. The invention ur-thermore concerns a process for the manufacture of such a molded article wherein a molding composition of a resin (e.g. synthetic) containing at least one peroxidically crosslinkable component and optionally, if desired,a filler and/or other adaitive, is used for forming a molded article; the article is formed for example by rolling, calendering, injec-tion-molding, extrusion, pressing, extrusion blow molding, coating, spread-coating, or the like.
It is known that it is possible to alter the properties of resins (e.g. synthetic) by crosslinking; for example, physical properties, such as strength, elasticity, and also aging re-sistance can be considerably improved. Depending on the resins (e.g. syntheticl, crosslinking can be accomplished by irradiation with high-energy rays, or by chemical methods by means of sulfur, selenium, tellurium, peroxides, aromatic polynitro and polyamino compounds, as well as quinol derivatives.
The positive properties attainable, on the one hand, with the crosslinking of a resin (e.g. synthetic~, such as improvement in strength, especially at an elevated temperature, are, however, achieved at the cost of still other, not always desirable accompanying characteristics, among which is, in particular, the loss of weldability in the case of thermoplastic resins (e.g. synthetic). Crosslinked resins (e.g. synthetic) cannot be welded to an ade~uate extent either thermally or by means of swelling welding agents or solvents. In this case, normally specific adhesion promoters must then be employed.
- Numerous technical fields of application exist, however, where a maximally simple joining technique for molded articles, ~

0 ~ .~
resins (e.g. synthetic) ~g de~irable, but which joinin~ technique cannot be utilized in the case of crosslinked resina (e.g.
synthetic). This is evident, for example, in the area of sealing sheets of resins (e.g. synthetic) for building construction and oxcavation-typc cons~ruc-~ion, as comprchcnsively disclosed, for example, in DOS ~German Unexamined Laid-Open Application~

2,628,741.
Conventional thermoplastic sealing sheets based on soft polyvinyl chloride, polyisobutylene, acrylic polymers, or bitumen-modified thermoplastics can be tightly welded together along the seam beads in a simple and perfect fashion, but exhibit the disadvantages of temperature sensitivity, of soften-ing, and tendency toward cold flow. Efforts have been made to counteract these disadvantages by laminating reinforcing inserts of, for example, fabrics or mats of textile fibers or glass fibers onto or into the sheets. The known sealing sheets,-on the-other hand, which are made of vulcanizable synthetic resins, for example those based on chloroprene elastomer, ethylene-propylene-diene terpolymers, chlorosulfonated polyethylene elastomer, or butyl rubber, do satisfy the mechanical strength requirements and are weatherable, but display the disadvantage that the vulcanized sealing sheets cannot be welded together and can be bonded permanently with the aid of adhesives or adhesive tapes in a firm connection only with difficulties;
see, for example, DOS 2,510,162, or D~S ~German Published Application~ 2,233,199.
An intermediate position is occupied by sealing sheets based on thermoplastic resins (e.g. synthetic) with elastomeric properties. In the sealing sheet according to DOS 2,621,~25, for example, the final vulcanization is to take place only after laying on the site and aEter establishment of the seam joints between the sealing sheets; however, there is the ~ ~65083 danger of premature vulcanization whereby then the simple - manufacture o~ welded seam joints is, in turn, made impossible.
Moreover r during subsequent repair work, it is no longer pos-sible to conduct a weldin~ operation.
Recently, the practice has also been adopted of producing, instead of the precedingly described one-layer resin (e.g. synthetic) sealing sheet built up homogeneously of one material (and optionally equipped with a reinforcing lnsert), multilayer sealing sheets of vulcanizable materials, wherein only an inner layer contains a vulcanization accelerator, and the outer layer is free of vulcanization accelerator and thus can still be welded together thermally and/or by solvents or by swelling welding agents; see DOS 2,628,741.
One disadvantage in these multilayer sealing sheets is, the increased technical building-up work, i.e. three in-dividual films must be produced which, in additional process steps, must be laminated together without the occurrence of premature vulcanization, so that the desired product can be obtained. This product is to exhibit, on the one hand, suf-ficient mechanical strengths, even at elevated temperatures,and, on the other hand, is to permit a joining technique with the use of welding.
However, for molded articles other than sealing sheets, it can be desirable and advantageous to provide them with other properties, in addition to the properties of a resin (e.g. synthetic) attainable on the one hand only by cross linking, which additional properties usually prevail only in the non-crosslinked condition of a resin (e.g. synthetic).
The thermoplastic mixture proposed in DAS 2,202,73~ aims in this direction; the mixture is intended for the production of molded articles, wherein a vulcanizable, rubbery mixed polymer is homogeneously distributed in a thermoplastic mixture, and ....

~ ~6~3 this mixture in total is vuIcanizéd only partially , i.e. not completely . This incomplete vulcanization is attained by a correspond~ingly low addition of vulcanizing agent . The thus-obtained , thermoplastic mixtures still exhibit limiked ther moplastic properties besides elastomeric properties . The weldability , however , is no longer present in these mixtures , either .
It would be advantageous to have a molded article of a resin (e.g. synthetic) which , on the one hand , displays the advantegeous properties effected by the crosslinking of a resin (e.g. synthetic) and, on the other hand , also still exhibits the weldability of the thermoplastics required for a simple joining technique . The present invention proposes a molded article of the type mentioned in the foregoing wherein a peroxidically crosslin]cahle component is present in the molded article in homogeneous distribution , and is peroxi-dically crosslinked in part of the molded article , including a portion of the surface of the molded article .
The present invention provides a molded article made from , a resin molding composition (i) containing , homogeneously distributed therein , 2 to 25o by weight , based on the weight of the resin molding composition~
of a suitable component capable of dissolving or swelling a peroxide crosslinking agent , and (ii) containing , homogeneously distributed therein , at least 1~ by weight , based on the weight of the resin composi-tion , of at least one peroxidically crosslinkable component, said peroxidically crosslinkable component , in part of the , ~ 4 -molded article wh,lch,includes part of t'ne surface oE -the molded article , being crosslinked by reaction with said peroxide crosslinking ayent .
The present invention also provides a molded article made Erom , a resin molding composition (i) containiny , homogeneously distributed therein , 2 to 25% by weight , based on the weight of the resin molding compositlon, of a suitable component capable of dissolving or swelling a peroxide crosslinking agent, and (ii) containing , homogeneously distributed therein , at least l~ by weight , based on the weight of.the resin composition , of at least one peroxidically crosslinkable compo-nent , said peroxidically crosslinkable component , in part of the molded article , which includes at leas-t part of the surface of the molded article , being crosslinked by reactio~. with 2'0 said peroxide crosslinking agent .
The present invention in accordance with another aspect provides a process for the production of a molded article made from , a resin molding composition (i) containing , homogeneously distributed , ~ therein , 2 to 25% by weight , based on the weight of the resin molding composition , of a suitable component capable of dissolving - - or swelling a peroxide crosslin]cincJ agen-t , ,, 30 a.nd (ii) conta,i~,ing , hvmogeneously distributed , therein , a-t ~.east 1% by welyht , based on .~
.,.
~. - 5 -" ..

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the weight of ~he resin composition, of at least one peroxidic~lly crosslinkable compo-nent , sa.id peroxidically crosslinkable component , in part of the molded article which includes part of the surface of the molded article , being crosslinked by reaction with said peroxide crosslinking agent , wherein a molded article is forrned from a resin molding composition as defined above and characterized in that a liquid peroxide crosslinking agent or a peroxide crosslinking agent solution is applied to part of the surface of said molded article , then said perodixe crosslinking agent is allowed to migrate into the molded article until a desired migration depth is reached and thereafter a peroxidic crosslinking step is performed .
The present invention also provides a process for the production of a molded article made from , a resin molding composition (i) containing , homogeneously distributed therein , 2 to 25% by weight , based on the weight of the resin molding composi-tion , of a suitable component capable of dissolving or swelling a peroxide crosslinking agent , and (ii) containing , homogeneously distributed therein, at least 1% by weight , based on the weight of the resin composition , oE at least one peroxidically crosslinkable component , said peroxidically crosslinkable component , in par-t oE the molded article which includes at leas-t part of the surface ~f the molded article , being c~osslinked by reaction with : - 5 a -., ~

said peroxide crosslinkihy ageni , wherein a molded article is formed from a resin molding composition as defined above and characterized in that a liquid perox~de crosslinkin~
agent or a peroxide crosslinking agent solution is applied to at least part of the surface of said molded article , tllen said peroxide crosslinking agent is allowed to migrate into the molded article until a desired mi-gration depth is reached and thereafter a peroxidic crosslinking step is performed .
. As indicated above , the present invention provides , in brief :
(a) a molded article made of a resin molding composition consisting of or containing at least one peroxidically crosslinkable component , characterized in that said peroxidically crosslinkable component is present in the molded article in a homogeneous distribution and in that the peroxidically crosslinkable component , in par-t of the molded article which includes at least part of the surface of the molded article is crosslinked by reaction -with a peroxide crosslinking agent ;
(b) a molded axticle made of a resin molding composition consistiny of or containing at least one peroxldically crosslinkable compo-nent, characterized in that said peroxidically crossllnkable component is present in the molded article in a homogeneous distribution and in that the peroxidically crossllnkable component , in part of the molded art.icle which incl.udes part of the surface of the molded article , ls crosslinked by rea.ction wlth a peroxlde crosslinklng agent ;
(c) a, process fox the production.of a molded ar-ticle as - - 5 b -, !

l 1~S083 defined above wherein a mol.ded article is formed from a resin molding composition consistiny of or containing at least one peroxidically crosslinkable component homo-geneously distributed therein and characterized in that a peroxide crosslinking agent is applied to at least part of the.surface of the molded article , then said peroxide crosslinking agent is allowed to migrate into the molded article until a desired depth i5 reachea and thereaf-ter a peroxidic crosslinking step is performed ; and (d) a.process for the production of a molded article as clefined above wherein a molded article is formed from a resin molding composition consisting of or containing at least one peroxidically crosslinkable component homogeneously distributed therein and characterized in that a peroxide crosslinking agent is applied to part of the surface of the molded article , then said peroxide crosslinking agent is allowed to migrate into the molded article until a desired migration dpeth is reached and thereafter a .peroxide crosslinking step is performed .
The molded article of this invention has the ad~antage that it starts with a single , homogeneous material batch and can be processed uniformly , and yet exhibits , in separate zones , on the one hand the properties of the non-crosslinked (synthetic) resin, such as weldability , elasticity , and, on the other hand , the properties of the . resin (e.g. synthetic) obtainable by crosslinking , such as incr-ased strength , abrasion resistance , chemical resistance .

.
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- , - 5 c -.
', 0 ~ 3 The invention provides a homogeneous, crossli~kable molded article which, however, contains the crosslinkin~ agent, a peroxide, only in those regions which are to be crosslinked.
In this connection, the part or region to be crosslinked can be Ereely selected wi~hin wide limi-ts in dcpcndence on the moldcd articleO Preferably, the molded article is at least partially crosslinked, starting with one side of its surface ~e.g. a major surface in the case of a sheet or plate) over a portion of its thickness. With the use o~ a resin (e.g. synthetic) weldable in the non-crosslinked condition thermally and/or by solution welding or swelling welding agents, the molded article of this invention can then also still be welded on a surface which has remained without crosslinking, by thermal process and/or by solution welding or swelling welding agents, in contrast to the crosslinked surface zone which has lost its weldability by the crosslinking process. Alternatively, it is possible to crosslink the entire surface of the article in which case it will be necessary to expose the uncrosslinked material by some suitable means such as cutting on scrapping prior to welding.
According to the present invention the peroxidically crosslinkable component may correspond to the resin o~ the molding composition or is contained additionally to -the (synthetic) resin in the molding composition.
The following polymersare preferably employed as the peroxidically crosslinkable component:
ethylene-propylene terpolymer ethylene-propylene copolymer natural rubber styrene-butadiene elastomer polybutadiene elastomer polyisoprene elastomer polyethylene

3~50~

e-thylene-vinyl acetate acrylonitrile-butadiene-styrene styrene-butadiene-elastomer block copolymer styrene-isoprene-elastomer block copolymer neoprene elastomer nitrile elasto~ler polysulfide elastomer chlorinated polyethylene polyurethane vinylidene copolymer silicone elastomer vinyl-silicone elastomer polyacrylate chlorosulfonated polyethy]ene or fluorosilicone elastomer~
Blends of the aforementioned polymers with one another, as well as with materials not crosslinkable by means of a peroxide can be utilized, in total, for the molding composition. To produce molded articles according to this invention, the molding composition preferably, should contain at least 1~ by weight of a peroxidically crosslinkable component. On the other hand, the molded article can be made exclusively of peroxidically cross- -linkable component, i.e. from corresponding polymers and/or blends of such polymers with one another. The molded ar-ticle can more-over optionally contain fillers, e.g. carbon blacks, chalk, plasticizers, stabilizers, antiaging agents, coloring agents, mold lubricants, etc. Also the use of blowing agents is possible, so that ~oamed molded articles can be manufactured, with a struc-ture according to this inventlon. The molded article proper can be produced conventionally, for example by extrusion, rolling, calendering, injection-molding, pressing ~press-molding~, ex-trusion blow molding, coa-ting, spread-coating, and other known ~7--..
, 1 1~5~3 process techniques. The molded article can also be joined to further layers and/or molded parts, to form multilayex articles.
The article can also contain reinforcing inserts~
According to the present invention the peroxidically crosslinkable component may comprise crosslinkable monomers including monomers of acrylates, methacrylates, diallylphthalate, and triallylcyanurate.
A preferred embodiment according to this invention relates to flat articles, such a6 films, sheets, plates or panels, and especially the construction of sealing sheets of a resin (e.g. synthetic) which are resistant to the effects of water and weathering. I-t is possible, by utilizing the presen-t invention, to provide a sealing sheet for tight sealing pur-poses which, on the one side, is still weldable and thus permits a simple and safe joining techni~ue, and which otherwise exhibits the properties of the crosslinked resin (e.g. synthetic~, especially properties such as weatherability and high tear strength at elevated temperatures. As the resins (e.g. syn-thetic), in particular, and also as the peroxidically cross-linkable resins (e.g. synthetic) for providing molded articles in the form of sealing sheets, elastomeric copolymers made of ethylene-propylene terpolymers or ethylene-propylene copolymers are preferably utilized.
It may be expedient for a practical usage of the molded articles according to the invention to mark the surface zones of the molded article which have been crosslinked and/or which have remained without crosslinking. This can be done, for example, by embossing, imprinting, or dye~marking a cor-responding sur~ace zone to render it recognizable.
Additional examples of forms of the molded article of this invention are, for instance, profiles or other forms, such as banisters, bumpers, decorative moldings, etc., which are to be jolned, for example, with additional materials to form a composite article. In this connection, a crosslinked zone of the molded article can cons-titute the outside surface exposed to stress, with, for example, a high abrasion resistance, whereas the non-crosslinked surface zone is connected to an understruc-ture, for example by welding or laminating.
The present invention also provides as indicated above, for a process for the manufacture of the aforedescribed molded article of this invention. The starting material as suggested above is a molding composition of a resin (e.g. synthetic) containing at least one peroxidically crosslinkable component and optionally, if deslred, a fil:ler an~/or other addltive,j from which a molded article is shaped, or example, by rolling, calendering, injection-molding, extrusion, press-molding, ex-trusion blow molding, coating, spread-coating, or the like.
~ ccordincJ ~o the inventlon, the provislon ls mad~
that peroxide is applied at least over a portion of the surface of the molded article, then the peroxide is allowed to migrate into the molded article until a desired migration depth has been reached in the molded article, and subsequently the per-oxidic crosslinking step is performed.
The process of this invention has the advantage thatwith a molded article, which can be manufactured even in only a single production step and which is made from a batch which is homogeneous with regard to the material, it is possible after the molding of such article to crosslink part thereof at any desired point in time, whereas the remainder of the molded article remains non-crosslinked. The crosslinking depth attain-able, corresponding to the miyration depth of the peroxides, is dependent on the peroxide selected as well as on the molding composition, and also on the amount of time expended~ The mi~ration velocity and the migration depth can, however, be positively affected along the lines of conducting the process of this invention, as will be explained in greater de-tail below.
One advantageous fur-ther developm0nt of the process of this invention provides that liquid or dissolvéd peroxide is applied.
Depending on whether the peroxide is in the liquid or crystal-line phase at the processing temperature, the sa~e dissolving solvent can be added to the peroxide, preferably in a ratio of peroxide to solvent of between 100 : 0 to ~0 : 50 (in parts by weight). In a further development of the invention, es-pecially suitable solvents for the peroxides are agents from ` the group of the extender oils, stabilizing agents and/or _g_ , . . .

, ~ .

~ ~50~33 plasticizers. Usable extender oils as solvents for the peroxide are, for example, alkylated benzenes, as well as paraffinic and naphthenic mineral oils. The alkylated benzenes with a branched alkyl chain have the advantage, in this connection, that they do not consume any free radicals during crosslinking, but they exhibit the disadvantage of a relatively high volatility and in this regard are less well suitable for molded articles utilized at relatively high temperatures. The highly refined mineral oils of a paraffinic or naphthenic type, in contrast thereto, consume free radicals during crosslinking, so that an increased proportion of peroxide must be used to obtain the same degree of crosslinking desired. Other suitable solvents for the peroxide are stabilizing agents or plasticizers, wherein these can be identical, such as, for example, dimethyl phthalate or dibutyl phthalate.
The migration process of the peroxide into the molded article can be further promoted by providing that the molding composition itself contains an ingredient or component capable of dissolving,partially dissolving, or swelling the peroxide being considered. Therefore, it is suggested according to the invention to add to a molding composition, prior to the produc-tion of the molded article, substances which dissolve or swell the peroxide, said substances likewise stemming from the group consisting of extender oils, such as alkylated benzenes, paraf-finic and naphthenic mineral oils and/or plasticizers, such as phthalate plasticizers and/or crosslinkable monomers, such as acrylates methacrylates, diallyl terephthalate, triallyl cyanurate, ethylene glycol dimethacrylate, preferably in a quantity from 2 to 25%
by weight, based on the molding composition. These agents promote the migration of the peroxide into the molded article and make it possible to reach a desired migration depth within an adequate period of time.

. .

~ ~B~a83 According to a further pre~erred Eeature of the present invention another substantial improvement in the process and a promotion of the migration velocity can be at-tained by accelerating the migration of the peroxide by supplying hea-t, wherein the molded article is heated at mos-t to a tempera-ture lying at least 20 C below the decomposition temperature of the peroxide employed. The temperature treatment during the migration process is a decisive factor for shortening the required migration time, which amounts depending on the com-position of the molding batch and on the selected peroxide toonly a few minutes up to hours, at migration depths of between 100 and 1000 ~.
Among the conventional peroxides, especially suitable for this process according to the invention are the alkyl peroxides, peresters, diacyl peroxides, or peroxy ketals. The factors to be considered when selecting the peroxide are, besides a high reactivity with respect to the correspondingly chosen, crosslinkable polymers, a good solubility in a solvent or other migration vehicles, also a maximally low molecular weigh-t. For-.
it has been discovered that, the lower the molecular weight of the peroxide selected, the hi~her the migration velocity attainable and thus the greate.r the migration depth desired, obtainable within an adequate period of time.
For the application of the peroxide and/or of the peroxide solution, the conventional printing processes can be employed, such as copper plate printing rcopper gravure print-ing~, screen printing, spraying methods, and other application processes, such as casting methods, mist deposition processes, spreading processes~ or dipping processes, depending on the molded article and the purpose for which it is utilized.
Preferably, the peroxide or the peroxide solution is applied according to this invention in a layer of 15-150 g/m2. The ~ ~s~
weight per unit area of the thus-applied layer depends, in this connection, likewise on the application method selected. By means of the process of this in~ention, the peroxidic cross-linking step is preferably carried out on surface layers of molded articles, especially also oE flat articles, in a thickness starting with 100 ~ up to pre~erably 1000 ~.
Once the desired migration depth of the peroxide has been reached in the molded article, the peroxidic cross-linking step can be performed using the systems as customary, for example, in the rubber-processing industry, namely at temperatures in the range between 130 C and 220 C, depending on the respectively utilized type of peroxide. When using vulcanizing processes, care must be taken that the operation is carried out under the exclusion of atmospheric oxygen, since otherwise, due to oxygen inhibition, tacky surfaces of the molded articles result. This danger does not exist when employing microwave vulcanization.
Molded articles produced according to the process of this invention exhibit the advantage of increased tear strength at higher temperatures while retaining weldability with the use of solvents and/or thermal weldability, of increased solvent resistance on the crosslinked surface/ and of an increased abrasion resistance in these regions.
The invention will be explained in greater detail with reference to the drawing and to embodiments. In the drawing:
Figure 1 shows a cross section through a plate-shaped, homogeneous, non-crosslinked molded article, Figure 2 shows the cross section o~ the molded article according to Figure 1 after crosslinking, and Figure 3 shows, in a cross~sectional view, a seam connection of molded articles according -to the invention.

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a~3 E'igure 1 shows schematical~y a cross section of a plate-shaped, not yet crosslinked, homogeneous molded article 1 of a resin (e.g. synthetic) molding composition, wherein a peroxidically crosslinkable component is contained in the resin (e.g. synthetic) molding composition, for example an EPDM.
Depending on the function of the molded article and the desired degree of crosslinking, the crosslinkable component can amount to between 1 and 100% by weight of the molded article 1. It can be seen from the illustration of Figure 1 that the peroxide layer 2 in the form o~ a peroxide solution has been applied to the plate-shaped molded arkicle only over a portion of i-ts surface, namely on surface side A, i.e. a major surface.
Figure 2 shows the molded article produced according to the invention in its final condition, wherein the peroxide solution 2 has migrated into the molded article 1 up to a depth 5 and has thereater been crosslinked. The molded article ~1 at this stage exhibits the peroxidically crosslinked zone lA and the zone lB which has not been crosslinked. The degree of crosslinking attained in zone lA depends, as discussed above, on the proportions of crosslinkable component and on the type of crosslinking performed.
By choosing for the molded articles in the non-crosslinked condition weldable, i.e. thermally weldable resins (e.g. synthetic), or synthetic resins whlch can be welded by the use of solvents or swelling agents, then the molded articles, crosslinked only in partial zones according to the invention, also offer the possibility to utilize joining techniques with the aid of welding bonds. On example is illustrated in Figure 3, showing a lap weld seam. In this case, the non-crosslinked surface zones lB are joined together in the overlapping zone of two molded articles 1, and these surface zones are welded together, see weld seam 3.

a ~ ~

The manufackure of particular embodimerlts of the molded article accordirlg to -this i.nvention will be described with reference to the ollowiny examples:

Production of a sheet from e-thylene-prop~lene ter-polymer peroxidically crosslinked only over a portion of its thickness, starting from one surface side.
In an internal mlxer with floating weight ~anbury kneader~, the recipe components set forth below are mixed at 170 C:
100 parts by weight of EPDM " Keltan*" 712 from DSM
1 parts by weight of stearic acid 60 parts by weight o-f carbon black, FEF
40 parts by weight of silicic anhydride and kaolini-te (" SilithiA" ) 60 parts by weight of paraffinic mineral oil (" Sunpar"
150 from Sun Oil Company) 5 parts by weight of zinc oxide ' For purposes of improved homogenization, the thus-20 obtained material is introduced into a rolling mill for another 10 minutes at 180 C and therea-fter fed to the calender via a strainer. A sheet of a thickness of 1.2 mm produced therein at 180 C.at a rate of 5 m/min is then sprayed repeatedly on one side with the peroxide solution set forth below in a spraying plant., and dried:
20 parts by weight of dicumyl peroxide, 95% strength 20 parts by weight of mineral oil (" Sunpar*" 150) The application weight i.s about 50 g/m2. The -thus-sprayed sheet is subsequently dried at a -tempera-ture of 80 C
for a period of 4 hours. Thereaf-ter the thus-trea-ted sheet is vulcani~ed in a press for 20 minutes at 180 C and under a pressure of 20 kp/cm2.

* Trademark -14-a ~ 3 After the sheet has been produced, it is crosslinked on one side in a depth o up to 800 ~; the remain~er o~ the sheet is not crosslinksd. On the side which has remained without crosslinking, the sheet can be welded with a high~test gasoline-toluene mixture. The sheet, crosslinked in partial zones ac-cording to the invention exhibits a tear strength at 80 C of 5.9 N/mm2. The sheet which is entirely devoid of crosslinking, in contrast thereto, exhibits a tear strength of 0.12 N/mm2 at 80 C.

Under the same process conditions as described in - Example 1, a sheet having a thickness of 1.0 mm is produced from the following recipe, devoid of fillers:
100 parts by weight of EPDM/" BUNA "AP 451 from Chemische Werke Huls 5 parts by weight of zinc oxide l part by weight of stearic acid 140 parts by weight of paraffinic mineral oil/Gulf - Oil 2212

4 parts by weight of " Polywachs" 600 The thus-obtained sheet is coated on one side with 30 g/m2 of the following peroxide solution:
50 parts by weight of l,l-di-tert butylperoxy-3,3,5-trimethylcyclohexane 50 parts by weight of phthalate plasticizer (butyl benzyl phthalate) The thus-coated sheet is then dried at a temperature of 60 C for 4 hours in a drying chamber and, during this time, the peroxide migrates into the sheet. ~'hereafter the sheet is vulcanized in a press at 180 C and under 20 kp/cm for 20 minutes. In this way, a sheet is obtained which is unilaterally crosslinked to a depth of about 250 ~; this sheet i5 still * Trademark -15-weldable on the non-crossl:Lnked side and displays a teax strength at 80 C of 1.0 N/mm2. The sheet, not yet crosslinked, had a tear streng-th at 80 C of 0.09 N/mm2.

~ soft PVC shect having a thickness of 1.5 mm is produced from a recipe o~ the following composition:
50 parts by weight of E-PVC, K-value 70 20 parts by weight of bulk PVC, K-value 65 25 parts by weight of benzyl butyl phthalate 1.5 part by weight of barium cadmium stabilizer 6.0 parts by weight of hexanediol diacrylate 2.0 parts by weight of exposidized soybean oil The thus-obtained soft PVC sheet is coated on one side with tert-butylperoxybenzoate, 30 glm2, and then dried during a period of 2 hours at 60 C. During this time, the peroxide migrates into the sheet. Subsequently the sheet is exposed for 3 minutes to a temperature elevated to 190 C, thus performing the peroxidic crosslinking of the monomeric acrylate.
In this way, a sheet is obtained crosslinked only on one side in a layer thickness of about 200 ~. On this side, the sheet is substantially more solvent-resistant. In paring tests, the subsequent gel test in tetrahydrofuran yielded 36~
insoluble material in the crosslinked layer, whereas the non-crosslinked side was fully soluble.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A molded article made from, a resin molding composition (i) containing, homogeneously distributed therein, 2 to 25% by weight, based on the weight of the resin molding composition, of a suitable component capable of dissolving or swelling a peroxide crosslinking agent, and (ii) containing, homogeneously distributed therein, at least 1% by weight, based on the weight of the resin composition, of at least one peroxidically crosslinkable component, said peroxidically crosslinkable component, in part of the molded article which includes part of the surface of the molded article, being crosslinked by reaction with said peroxide crosslinking agent.

2. A molded article as defined in claim 1, characterized in that said molded article has the form of a sheet or a plate.

3. A molded article as defined in claim 2, characterized in that the peroxidically crosslinkable component is crosslinked over part of the thickness of the molded article.

4. A molded article as defined in claim 2, characterized in that said surface part consists of a major surface of said molded article and in that the peroxidically crosslinkable component is crosslinked over part of the thickness of the molded article.

5. A molded article as defined in claim 2, characterized in that said resin molding composition in the crosslinked condition can be welded thermally, by means of a solvent, by means of a swelling agent or by a combination thereof and in that the par-t of the surface of said molded article, which is not crosslinked, is weldable.

6. A molded article as defined in claim 2, characterized in that said peroxidically crosslinkable component is a polymer selected from the group of polymers consisting of ethylene-propylene terpolymer elastomer, ethylene-propylene copolymer elastomer, natural rubber, styrene-butadiene elastomer, polybutadiene elastomer, polyisoprene elastomer, polyethylene, ethylene-vinyl-acetate, acrylonltrile-butadiene-styrene, styrene-butadiene elastomer block copolymer, styrene-isoprene elastomer block copolymer, neoprene elastomer, nitrile elastomer, poly-sulfide elastomer, chlorinated polyethylene, polyurethane, vinylidene copolymer, silicone elastomer, vinyl-silicone elas-tomer, polyacrylate, chlorosulfonated polyethylene and fluoro-silicone elastomer and in that said component capable of dissolving or swelling said peroxide crosslinking agent is selected from the group of substances consisting of extender oils, crosslinkable monomers, plasticizers and mixtures thereof.

7. A molding composition as defined in claim 6, characterized in that said molding composition contains one or more fillers and/or other suitable additives.

8. A molded article as defined in claim 7, characterized in that the part of the surface of said molded article which is not crosslinked is weldable, thermally, by means of a solvent, by means of a swelling agent or by a combination thereof.

9. A molded article as defined in claim 8, characterized in that the peroxidically crosslinkable compo-nent is crosslinked over part of the thickness of the molded article.

10. A molded article as defined in claim 9, characterized in that said part of the surface of the molded article is a major surface of said molded article.

11. A process for the production of a molded article made from, a resin molding composition (i) containing, homogeneously distributed therein, 2 to 25% by weight, based on the weight of the resin molding composition, of a suitable component capable of dissolving or swelling a peroxide crosslinking agent, and (ii) containing, homogeneously distributed therein, at least 1% by weight, based on the weight of the resin composition, of at least one peroxidically crosslinkable com-ponent, said peroxidically crosslinkable component, in part of the molded article which includes part of the surface of the molded article, being crosslinked by reaction with said peroxide crosslinking agent, wherein a molded article is formed from a resin molding composition as defined above and characterized in that a liquid peroxide crosslinking a-gent or a peroxide crosslinking agent solution is applied to part of the surface of said molded article, then said peroxide crosslinking agent is allowed to migrate into the molded article until a desired migration depth is reached and thereafter a peroxidic crosslinking step is performed.

12. A process as defined in claim 11, characte-rized in that said molded article has the form of a sheet or a plate.

13. A process as defined in claim 12, characte-rized in that said surface part consists of a major surface of said molded article.

14. A process as defined in claim 12, charac-terized in that said peroxide crosslinking agent is applied in a layer of 15 to 150 g/m2.

15. A process as defined in any one of claims 12, 13 and 14, characterized in that the ratio of said peroxide crosslinking agent to solvent is between 100:0 and 40:50.

16. A process as defined in any one of claims 12, 13 and 14, characterized in that a peroxide crosslinking agent solution is applied and in that said peroxide cross-linking agent is dissolved in a solvent selected from the group consisting of extender oils, stabilizing agents, plas-ticizers and mixtures thereof.

17. A process as defined in any one of claims 12, 13 and 14, characterized in that the migration of said peroxide crosslinking agent is accelerated by supplying heat, wherein the molded article is heated at most to a temperature lying at least 20°C below the decomposition temperature of the peroxide crosslinking agent utilized.

18. A process as defined in any one of claims 12, 13 and 14, characterized in that said peroxide crosslinking agent is selected from the group consisting of alkyl peroxides, peresters, diacyl peroxides and peroxy ketals.

19. A process as defined in any one of claims 12, 13 and 14, characterized in that said peroxide crosslinking agent has a low molecular weight.

20. A process as defined in any one of claims 12, 13 and 14, characterized in that said peroxide crosslinking agent is applied by a printing method, casting method, mist deposition method spreading method or dipping method.

21. A process as defined in any one of claims 12, 13 and 14, characterized in that said peroxide crosslinking agent is applied by copper plate printing, screen printing or spray printing.

22. A process as defined in claim 12, charac-terized in that said peroxidically crosslinkable component is a polymer selected from the group of polymers consisting of an ethylene-propylene terpolymer elastomer, ethylene-propylene copolymer elastomer, natural rubber, styrene-butadiene elasto-mer, polybutadiene elastomer, polyisoprene elastomer, polyethy-lene, ethylene-vinyl acetate, acrylonitrile-butadiene-styrene, styrene-butadiene elastomer block copolymer, styrene-isoprene elastomer block copolymer, polysulfide elastomer, chlorinated polyethylene, polyurethane, vinylidene copolymer, silicone elastomer, vinylsilicone elastomer, polyacrylate, chlorosulfo-nated polyethylene and fluorosilicone elastomer, and in that said component capable of dissolving or swelling said pero-xide crosslinking agent is selected from the group consisting of extender oils, crosslinkable monomers plasticizers and mixtures thereof.

23. A process as defined in claim 12 characterized in that said crosslinkable component is a polymer selected from the group of polymers consisting of an ethylene-propylene terpolymer elastomer, ethylene-propylene copolymer elastomer, natural rubber, styrene-butadiene elastomer, polybutadiene elastomer, polyisoprene elastomer, polyethylene, ethylene-vinyl acetate, acrylonitrile-butadiene-styrene, styrene-butadiene elastomer bolck copolymer, styrene-isoprene elastomer block copolymer, polysulfide elastomer, chlorinated polyethylene, polyurethane, vinylidene copolymer, silicone elastomer, vinyl-silicone elastomer, polyacrylate, chlorosulfonated polyethylene and fluorosilicone elastomer, and in that said component capa-ble of dissolving or swelling said peroxide crosslinking agent, is selected from the group of substance consisting of alkylated benzenes, paraffinic and naphthenic mineral oils, acrylates, methacrylates, diallyl phthalate, triallyl cyanurate, phtha-late plasticizers and mixtures thereof.

24. A process as defined in claim 23 characteri-zed in that the ratio of said peroxide crosslinking agent to solvent is between 100:00 and 40:50.

25. A process as defined in claim 24 characte-rized in that said peroxide crosslinking agent is dissolved in a solvent selected from the group consisting of extenders, stabilizers and mixtures thereof.

26. A process as defined in claim 25, charac-terized in that said peroxide crosslinking agent is selected from the group consisting of alkyl peroxides, peresters, diacyl peroxides and peroxy ketals.

27. A process as defined in claim 26, charac-terized in that said peroxide crosslinking agent has a low molecular weight.

28. A process as defined in claim 27, charac-terized in that the migration of said peroxide crosslinking agent is accelerated by supplying heat, wherein the molded article is heated at most to a temperature lying at least 20°C below the decomposition temperature of the peroxide utilized.

29. A molded article made from, a resin molding composition (i) containing, homogeneously distributed therein, 2 to 25% by weight, based on the weight of the resin molding composi-tion, of a suitable component capable of dissolving or swelling a peroxide cross-linking agent, and (ii) containing, homogeneously distributed the-rein, at least 1% by weight,based on the weight of the resin composition, of at least one peroxidically crosslinkable component, said peroxidically crosslinkable component, in part of the molded article, which includes at least part of the surface of the molded article , being crosslinked by reaction with said peroxide crosslinking agent.

30. A molded article as defined in claim 29, wherein said peroxidically crosslinkable component comprises crosslinkable monomers selected from the group consisting of acrylates. methylacrylates, dlallylphthalate and triallyl-cyanurate.

31. A process for the production of a molded article made from, a resin molding composition (i) containing, homogeneously distributed therein, 2 to 25% by weight, based on the weight of the resin molding composition, of a suitable component capable of dissol-ving or swelling a peroxide crosslinking agent, and (ii) containing,homogeneously distributed therein, at least 1% by weight, based on the weight of the resin composition, of at least one peroxidically crosslinkable component, said peroxidically crosslinkable component, in part of the molded article which includes at least part of the surface of the molded article, being crosslinked by reaction with said peroxide crosslinking agent, wherein a molded article is formed from a resin molding composition as defined above and characterized in that a liquid peroxide crosslinking agent or a peroxide crosslinking agent solution is applied to at least part of the surface of said molded article, then said peroxide crosslinking agent is allowed to migrate into the molded article until a desired migration depth is reached and thereafter a peroxidic crosslinking step is performed.