Laminates

Start of patent period: 1979 07 15 Longest possible duration:

© Issued on: 1980 02 25 © inventor:

© Dependency: '© Pamphlets considered to delineate the state of the art:

355,295

- 2 No.355295

The invention relates to a laminate in the form of a sheet or a strip of rubber composition, which is composed of a plurality of individual layers of a specific purpose rubber composition. The laminate can be made by any known method, for example calendering or the like; however, it is preferably formed by coextrusion, wherein two or more rubber compositions are passed through the preform of an injection mold to form individual layers, which are then combined in the final injection mold. A special method for this is described in US Pat. Nos. 3,497,425 and 3,557,265, which according to the cited patents are applied to plastic and thermoplastic elastomers for forming laminates.

Layered articles are known in which the individual layers consist of materials having different properties. Such articles have been used in the manufacture of tires wherein a rigid, partially vulcanized rubber composition is sandwiched between two layers of a soft, tacky, unvulcanized rubber stock by calendering the soft layers onto the already partially vulcanized mass. Strips of this type have been used as rubbing rubber strips in the bead area of ​​the tire where the tire touches the rim to avoid chafing between the tire and the rim.

An unvulcanized rubber composition tends to flow during vulcanization, thereby decreasing its actual dimension or thickness. This is especially true in the bead area and inner lining area of ​​the tire where the vulcanization pressure is high. In the above-described type of laminates in strip form, the partial pre-vulcanization of the rigid mass allows it to retain its dimension or thickness during tire curing, but the pre-vulcanization renders the strip dry, causing a sticking problem between it and the other parts of the tire during construction - and Vulkanisationsarbeitsgang caused. The outer layers of the soft, sticky, unvulcanized rubber composition in the laminate can overcome this deficiency and provide the necessary adhesion in the unvulcanized state, so that the laminate strip does not separate from the remaining parts of the tire before its final vulcanization. However, there is still an adhesion problem because layers (the outer layers) are adhered to a partially vulcanized layer.

In addition, these known strips were difficult and expensive to manufacture. During its production, the inner, stiff strip was calendered and partially hardened; then, to form the finished laminate, the soft, sticky strips were calendered on both sides of the then stiff strip. This process is costly and time consuming and requires several stages. Due to the limitations of calendering, it has also required the use of thicker strips for a reasonable safety margin than would have been necessary because of the desired properties of the final product.

The process and product of the invention have greatly simplified and improved the technology of laminates, thereby enabling their use not only in the prior art areas but also in areas not feasible prior to such development. Strips making use of the invention can be used in pneumatic tires as an air-impermeable lining covering the inner circumference of the tire, or as a friction rubber strip in the bead area of ​​the tire which contacts the edge of the rim when the tire is mounted and inflated will be used.

The technology according to the invention is not limited to these two places in a pneumatic tire. - It can be applied to many end products, such as conveyor belts and other industrial products.

The method and product of the invention are particularly useful where it is necessary for a material to retain a certain thickness in the final product. This has heretofore usually been achieved by using an excessive amount of material to ensure that the minimum is present in the final product after it has become thinner in the processing stages. The former partial Vorvulkanisationsmethode had despite a certain advantage but the disadvantage that only a partial vulcanization could be achieved. Full vulcanization would have rendered the vulcanized material unusable due to its poor adhesion.

The invention provides an improved laminate by selectively altering some of the layers in the laminate so that the layers are either partially vulcanized or fully cured,

- 3 Nr.355295 when exposed to radiation or remain unaffected by the radiation and unvulcanized.

This technique eliminates at least one of the steps required in the known process. In this technique, the laminate strip is obtained by calendering or, preferably, by coextrusion. The rubber stocks in the various layers are selectively sensitized or desensitized to react to different levels of radiation. The laminate strip is then exposed to radiation, whereby the sensitized layer (s) are partially or fully vulcanized and the desensitized layer (s) remain unaffected. Alternatively, all layers can be sensitized to varying degrees to vulcanize all layers to some extent in the composite, with various layers being vulcanized to varying degrees. This results in,

The aim of the invention is thus a laminate strip that can be made relatively cheap and uncomplicated.

In such a strip, the thickness of the individual layers is determined by the amount of layer necessary to fulfill their function, and not by the problems inherent in the manufacture of the strips.

In such a strip, some layers are sensitized to partially or fully vulcanize when irradiated and desensitize other layers so that they are unaffected by radiation; however, all layers can also be sensitized more or less so that they fully or partially vulcanize, so that the physical properties of the layers are different.

The invention thus relates to a laminate which has at least two layers of rubber compounds, which is characterized in that at least one of the layers contains a sensitizer which promotes crosslinking upon irradiation, so that the layers are crosslinked differently after irradiation.

The inventive method is that

a) providing at least one of the layers of the laminate with a sensitizer which promotes cross-linking upon irradiation,

b) the layers are joined together to form the laminate and

c) the laminate is irradiated, wherein the sensitized layer (s) at least partially crosslink and differ in the finished laminate, two or more layers in their degree of crosslinking.

For example, the inner liner in a pneumatic tire must be sufficiently air-impermeable to prevent the compressed air enclosed by the tire from entering the tire. When air gets into the tires, it will expand due to the heat generated during operation and eventually cause separation of the tire layers. The more air-impermeable materials, for example, the halogenated butyl rubbers, have no good stickiness and adhesion in the raw state, are soft, and become thin in high-pressure regions when the tire is expanded and vulcanized during vulcanization.

It is necessary that the inner liner be sufficiently impermeable to air and maintain its dimensional stability so that it does not become too thin in these high pressure regions of the tire to effectively stop the passage of air into the tire. It is also necessary that the inner liner be sufficiently tacky to adhere to the adjacent portions of the tire until the tire is cured. Heretofore, it has been necessary to provide an inner liner over the entire inner circumference of the tire that is thicker than necessary to effectively stop the passage of air to maintain the minimum thickness in the high pressure regions (tread shoulders) of the tire. The invention avoids the need to provide the thick inner lining on the entire circumference of the tire. When using a coextrusion technique for the tread, it is possible to extrude a fitted inner liner in which the thickness in the high pressure regions of the tire increases without increasing the thickness in the low pressure regions. This means a considerable saving in material, since each

- 4 - No.355295 necessary minimum amount of material over the entire circumference of the inner lining can be applied.

The invention also makes it possible to produce an inner lining in which the inner layers of the laminate impart certain properties to the entire laminate while the outer layers adhere well so that no separations occur prior to the vulcanization of the tire. This is accomplished by having one of the inner layers containing a halogenated butyl rubber which provides the necessary air impermeability, another inner layer containing a polybutadiene rubber compound which upon irradiation provides rigidity so as to retain its dimensional stability during the vulcanization process and an outer layer provided on both sides, which contains a natural rubber mass which is sufficiently sticky, to adhere to the adjacent components of the tire and in the connection region of the inner lining to itself. The two inner layers are sensitized to crosslink or cure on irradiation while the outer layers are desensitized so that this radiation treatment does not affect tack. This strip can thus be made with much smaller dimensions than the known strips, thereby saving a considerable amount of raw materials and costs.

The same technology is applicable to the rubbing rubber strip of a tire. This strip is located in the bead area of ​​the tire and comes into contact with the edge of the rim during tire operation. It is necessary for this strip to withstand the high abrasion experienced by the tire in this area from the edge of the rim. This strip usually consists of a hard, high modulus, rigid rubber composition to withstand these abrasive forces and must be of sufficient thickness to protect the tire. The stiffness and hardness inherent in the friction rubber strip results in a loss of tack which creates a sticking problem during tire building and curing. There is a period of time between the tire building process and the vulcanization process. It is necessary, that the tire parts have sufficient adhesion to each other so that the unvulcanized tire does not diverge during this waiting time or thereafter, when it is expanded during vulcanization. Also, the high pressures in the bead area of ​​the tire during vulcanization cause the friction rubber strip material to become thinner in certain areas. These difficulties are overcome by the invention. The rubbing rubber strip is made in accordance with the invention by laminating a strip of hard, high modulus, rigid rubber composition between two strips of sticky, soft rubber compound. The hard strip is sensitized to partially or fully vulcanize upon irradiation, and the two outer strips are desensitized, so that radiation does not affect their adhesive properties. The strip thus formed is irradiated to partially or fully vulcanize the hard strip, maintaining its dimensional stability during vulcanization of the tire. The two sticky outer strips prevent separation of the strip from the adjacent layers of the tire and are at the joint area.

The invention is not limited to these two particular embodiments but can be applied to other products such as liners for containers, hoses and fabric reinforcements for the manufacture of containers. It is possible to produce laminates with layers of different materials depending on the desired properties and the end use.

It has been found that various compounds accelerate the vulcanization of rubber compounds by radiation to varying degrees, and that various compounds are useful to retard or inhibit the vulcanization of rubber compounds by radiation. These promoters and retarders are classified as sensitizing or desensitizing agents. The type of rubber used in bulk is critical and determines the type of promoter or retarder. The type of promoter or retarder varies when different rubbers are used in the composition, and the amount of these compounds may vary depending on the type of rubber used or the dose of radiation the rubber composition receives.

In particular, it has been found that p-dichlorobenzene (PDCB) is an effective promoter for radiation vulcanization in rubber stocks. It has also been found that certain thioether polythiols are effective promoters. The specific polythiols that have been tested and found to be useful are given in Table I. Compound 2 given in this table was used in the following examples and is designated "TEPT".

Table I

Polythioether polythiols derived from triene-dithiol or triene-Hj S-polyaddition compounds

<td>connection</td><td>Thiol funct. SH equiv. / G</td><td>Idealized chemical Structure and derivative</td>

<td>1</td><td>0.0050</td><td>_RL L₍ 1 [s (ch₂)₃sh]₃</td>

<td></td><td></td><td>of cyclodocetries and 1,3-propanedithiol</td>

<td>2</td><td>0.0082</td><td>S [CH₂CH₂-J- -j- (CH₂CH₂SH)₂ ]₂</td>

<td></td><td></td><td>of trivinylcyclohexane and H₂S</td>

<td>3</td><td>0.0045</td><td>S {CH₂CH₂-J- - | - [CH₂CH₂S (CH₂)₂SH]₂}₂</td>

<td></td><td></td><td>of trivinylcyclohexane and ethanoldithiol</td>

<td>4</td><td>0.0041</td><td>| -J- [CH₂CH₂S (CH₂) ^ SH]₃</td>

<td></td><td></td><td>of trivinylcyclohexane and 1,4-butanedithiol</td>

<td>5</td><td>0.0049</td><td>Yourself₂)₂-F- -J - [(CH₂)₂-S- (CH₂)₃SH]₂1₂</td>

<td></td><td></td><td>of trivinylcyclohexane and 1,3-propanedithiol</td>

It has also been found that effective retarders of radiation vulcanization or crosslinking include aromatic oils, sulfur, sulfur vulcanization accelerators as well as some substituted-diphenylamine type rubber antioxidants and / or antiozonants, such as N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine , are.

Table II lists some commercial antioxidants / antiozonants that have been shown to be useful retarders of radiation vulcanization. A higher swelling ratio indicates a stronger delay effect. The swelling ratio was determined by mixing 1 part of the specific antioxidant in 100 parts of polybutadiene rubber, the mixture 5 megarads

- 6 - No.355295

Subjected to radiation, the sample immersed in toluene for 48 hours at room temperature and the mass of the swollen rubber measured against the mass of the dry rubber.

Table II

<td>sample</td><td>Antioxidants</td><td>swelling ratio</td>

<td>1</td><td>-</td><td>11.5</td>

<td>2</td><td>2,6-di-tert. butyl-p-cresol (D BPC)</td><td>15.1</td>

<td>3</td><td>4,4'-thiobis- (6-tert-butyl-m-cresol)</td><td>13.6</td>

<td>4</td><td>Phenyl-β-naphthylamine (PBNA)</td><td>14.7</td>

<td>5</td><td>syn di-0 -naphthyl-p-phenylenediamine</td><td>11.9</td>

<td>6</td><td>N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine</td><td>27.4</td>

The dose of radiation used according to the invention depends on various variables, namely the type of rubber in the rubber composition, the promoter or retarder used in the rubber composition, the amount of promoter or retarder used in the rubber composition, the thickness of the material layer, the thickness of adjacent material layers , the order of the layers of material, the number of layers of material and whether the radiation is allowed to act on one or both sides of the laminate. The proper combination gives the desired physical properties in the laminate strip.

The dosage can also be controlled by the amount of energy applied so that the rays do not penetrate the entire strip completely. This leads to the irradiation of a part, but not of the whole strip.

Fig. 2 is a partial section of a tire inner lining according to the invention, Fig. 3 is a partial section of a molded inner lining for tires, Fig. 4 is a fragmentary sectional view of another embodiment of the invention Fig. 5 is a section of a tire having a friction rubber strip and an inner liner according to the invention.

In Fig. 1, the laminate is generally designated -10- which has a stiff, sensitized inner layer -12- and two desensitized outer layers -11-. The inner layer is a rubber composition containing 100 parts of a styrene / butadiene solution copolymer, 80 parts of active carbon black, 4 parts of 2,6-di-tert-butyl-p-cresol, and other ingredients except for sulfur and sulfur vulcanization accelerators. The two outer layers -11- consist of a rubber composition containing 100 parts of natural rubber, 45 parts of carbon black and other ingredients including the following which retard radiation crosslinking: N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine , aromatic oil, sulfur and sulfur vulcanization accelerator.

According to the invention, the laminate -10- after its construction is subjected to a radiation treatment which cross-links the layer -12- but does not affect the layers -11-. The laminate is then placed in the final product, whereupon the processing to the final product, including the vulcanization thereof, in which the layers -11- are vulcanized but the layer -12- is not degraded, is carried out.

According to the invention, the laminate -10- can be obtained by calendering or coextruding. Coextrusion is preferred because it allows better control of layer thickness at smaller dimensions, provides better inter-layer adhesion, and permits the formation of laminates with contours at preselected locations as shown in FIG.

- 7 No.355295

To demonstrate the suitability of the invention, laminates were prepared comprising a layer of soft natural rubber composition containing 100 parts of natural rubber, 45 parts of carbon black and other ingredients such as N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine , aromatic oil, sulfur and sulfur vulcanization accelerator, all of which exert a radiation curing desensitizing effect, and a hard rubber composition layer containing 100 parts of a styrene / butadiene solution copolymer, 80 parts of active carbon black and 4 parts of 2,6-di-tert-butyl contains -p-cresol, a sensitizer. In this laminate, the soft natural rubber composition had a thickness of 0.1143 cm and the solution-styrene / butadiene hard mass had a thickness of 0.0889 cm. These layers were separated by two layers of polyethylene terephthalate and a blue cellophane dosimetry layer to measure the dose of radiation used. Two identical pairs of laminate samples were first irradiated on one side, turned over and then irradiated on the other side. After this irradiation, the laminates were disassembled. The layers of each pair of such strips were examined for physical properties (stress-strain values). These results are given in Table III under the column "Radiation Vulcanization". The separated layers of the remaining irradiated strips were subjected to additional thermal vulcanization for 10 minutes at 165 ° C, whereupon their physical properties were determined. These results are given in Table III under the column "Irradiation and Thermal Vulcanization". In this way, three independent studies were performed, each at a different dosage, as shown in Table III.

Table III

<td rowspan="2">test rubber compound</td><td colspan="2">Strahlungsvulkanisation</td><td colspan="2">Radiation and therm. vulcanization</td>

<td>desensitized natural rubber</td><td>sensitized Styrene-butadiene copolymer</td><td>desensitized natural rubber</td><td>sensitized Styrene-butadiene copolymer</td>

<td colspan="2">Test 1 Average dose 0.6 Hegarad</td><td></td><td></td><td></td>

<td>tensile strenght (N / cm¹)</td><td>407.12</td><td>1,579.41</td><td>1,971.81</td><td>1,706.94</td>

<td>Module (N / cm¹) at 100% stretch</td><td>30,90</td><td>392.40</td><td>196.20</td><td>462.05</td>

<td>200% stretch</td><td>51,70</td><td>889.77</td><td>551.32</td><td>1,255.68</td>

<td>300% elongation</td><td>103.00</td><td>1,540.17</td><td>1,098.72</td><td>-</td>

<td>Elongation at break (%)</td><td>560</td><td>300</td><td>445</td><td>260</td>

<td colspan="2">Test 2 Average dose 11 Hegarad</td><td></td><td></td><td></td>

<td>tensile strenght (N / cm¹)</td><td>579.77</td><td>1,805.04</td><td>1,991.43</td><td>1,167.39</td>

<td>Hodul (N / cm *) at 100% stretch</td><td>34.53</td><td>416.93</td><td>178.54</td><td>365.91</td>

<td>200% stretch</td><td>62,10</td><td>1,030.05</td><td>482.65</td><td>827.96</td>

<td>300% elongation</td><td>131.45</td><td>1,736.37</td><td>990.81</td><td>-</td>

<td>Elongation at break (%)</td><td>630</td><td>315</td><td>460</td><td>260</td>

- 8 No.355295

Table III (continued)

<td>test</td><td colspan="2">Strahlungsvulkanisation</td><td colspan="2">Radiation and therm. vulcanization</td>

<td>rubber aces</td><td>desensitized natural rubber</td><td>sensitized Styrene-butadiene copolymer</td><td>desensitized natural rubber</td><td>sensitized Styrene-butadiene copolymer</td>

<td colspan="2">Test 3 Average dose 12.3 Hegarad</td><td></td><td></td><td></td>

<td>tensile strenght (N / cm²)</td><td>589.58</td><td>1,687.32</td><td>1,785.42</td><td>1,412.64</td>

<td>Module (N / cm¹) at 100% stretch</td><td>37.87</td><td>486.58</td><td>152.06</td><td>420.85</td>

<td>200% stretch</td><td>68.96</td><td>1,206.63</td><td>475.79</td><td>982.96</td>

<td>300% elongation</td><td>141.26</td><td>-</td><td>892.71</td><td>-</td>

<td>Elongation at break (%)</td><td>595</td><td>265</td><td>455</td><td>265</td>

These details clearly show the advantages of the invention; they show that the sensitized layer is vulcanized by the radiation but the desensitized layer is not; the desensitized layer is vulcanized by the subsequent vulcanization, whereby the sensitized layer is not adversely affected by this subsequent vulcanization.

In Figure 2, the laminate is generally designated -20- has two outer layers -21- and two different inner layers -22 and 23- on. This embodiment demonstrates the application of the invention to a laminate containing at least three separate rubber compositions. The outer layers -21- which contain a soft rubber for good tackiness are desensitized to radiation by, for example, incorporating therein desensitizing agents such as N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine. The inner layer -22- is a relatively hard rubber composition based on polybutadiene rubber and reinforced with carbon black. It contains sensitizers (such as TEPT) that accelerate radiation crosslinking. This mass is vulcanized upon irradiation, so that it does not flow during subsequent processing steps. The mass should retain its thickness in the final product.

Layer -23- is also sensitized, for example by the sensitizer TEPT, to crosslink upon irradiation. This layer is impermeable to air and contains halogenated butyl rubber as a base. The layer should maintain its shape during the subsequent treatment and form a barrier to air access from the inner air chamber of a pneumatic tire into the tire body. This laminate is irradiated again after its construction and incorporated into the final product, which is then completed.

This embodiment of the invention is not limited to the layer sequence shown in FIG. One or more inner strips of different masses may be provided to meet certain requirements for the application of the laminate strip. For example, the layer -22- may be omitted from the laminate if the stiffness of the layer -23- by radiation crosslinking is sufficient to stabilize the dimension of the layer during subsequent processing. However, additional layers can be added to overcome other problems.

FIG. 3 shows another embodiment of the inner laminate -30- shown in FIG. In Fig. 3, the outer layers -31- again contain a soft rubber compound desensitized to radiation vulcanization and having good tackiness. The layer -32- is again a hard rubber layer which is sensitized to vulcanize upon irradiation. This layer consists of a solution butadiene rubber and active carbon black. The layer -33- is again

No. 9,55295 discloses a hard rubber layer containing a halogenated butyl rubber and active carbon black. These

Layer forms the barrier, which prevents the passage of air.

Fig. 3 shows a molded embodiment of the invention in which the layers -32 and 33- are thicker in a predetermined area of ​​the tire where the lining is subjected to the highest pressure during molding and vulcanization. In this embodiment, the thickness of each layer is maintained relative to the other layers over the entire width of the strip. The excessive thickness in this area prevents the innerliner from thinning and the carcass forming shadows (carcass cords beating through the thinner innerliner), which can happen in this area of ​​the tire. This shaped strip provides the required thickness in these difficult areas without having to be maintained along the entire width of the strip, as was previously the case.

Fig. 4 shows another embodiment of a laminate for the inner lining. In Fig. 4, the laminate is generally designated -40-. It has two outer layers -41- of a soft rubber composition which is said to have good tack and is desensitized to radiation vulcanization, for example by inclusion of an antioxidant such as N, 3-dimethylbutyl-N'-phenyl-p-phenylenediamine. Two intermediate layers -42 and 43- are arranged between layers -41-. These consist of a hard rubber composition containing halogenated butyl rubber and active carbon black, which has been sensitized for vulcanization by irradiation, for example by the addition of TEPT. Between layers -42 and 43- there is a layer -44- of polyisobutylene without sensitizing or desensitizing agent. This material optionally contains a reinforcing material, such as carbon black. Bridges -45 and 46- of the same material used in layers -42 and 43- connect layers -42 and 43- together. These bridges form pockets containing layer -44.

When the laminate of Fig. 4 is irradiated, layers -41- are left unaffected, ie soft and sticky, so as to ensure adhesion to the final product during subsequent processing. The layers -42 and 43- partially or completely vulcanize, forming a stiff, hard base for the laminate. The material in the layer -44- is degraded by chain scission and forms a liquid, pasty material. This composite can then be used as the inner lining of a tire and subjected to vulcanization. The obtained tire has an inner lining containing pockets of liquid polyisobutylene. This material acts as a seal on flat tires and gives the tire the ability to self-seal. Bridges -45 and 46- are needed

In the laminate of Figure 4, the radiation in the polyisobutylene causes chain scission, while the incoming crosslinking does not compensate for the degradation due to this chain scission reaction in this material. Standard butyl rubber, a copolymer of polyisobutylene and isoprene, is degraded to some extent by radiation, but this degradation is compensated for by the simultaneous crosslinking reaction. The same two Kompensierungsreaktionen occur in halogenated butyl rubbers with the difference that the crosslinking reaction in the halogenated butyl rubber is stronger than in the standard butyl rubber. This behavior of butyl rubbers demonstrates that radiation treatment and the selection of the right sensitizer or desensitizer for each specific rubber is critical.

It is also possible to apply this chain scission to crosslinks in a three-layer laminate in which the two outer layers are made of soft, tacky rubber masses desensitized for resistance to radiation vulcanization, and the inner layer is a mixture of polymers such as polyisobutylene and halogenated Butyl rubber, contains. Upon irradiation, the polyisobutylene is degraded to form a liquid which is trapped in the crosslinked halogenated butyl rubber. This composite has self-sealing properties.

Fig. 5 shows a tire according to the invention. The tire is designated -50- and has a tread -51-, side walls -52- and beads -53-. The friction rubber strip -10- shown in Fig.l is located in the bead area of ​​the tire where the tire touches the rim. The inner lining -20- described in FIG. 2 is arranged on the inner circumference of the tire 10 Nr.355295. The other features of the tire may be any of the known constructions (radial, diagonal, belted diagonal) for passenger cars, trucks, airplanes, off-road tires,

Be tractors or industrial tires.

Table IV shows the sensitizing and desensitizing effect of various compounds on a rubber composition of the following basic composition:

Solution Styrene / Butadiene Copolymer (SBR) 100 parts Activated Carbon Black (CB) 50 parts

Each comparison is listed under a test number. The first column gives the components in the above basic composition, the second column the module at different strains and the last column the average radiation dose to which each mass has been exposed. During the tests, the two masses were stacked together and irradiated. The masses were then separated and the physical properties determined.

Table IV

<td rowspan="2">test</td><td colspan="3">Modulus at stretch</td><td rowspan="2">Dose, Avg. megarads</td>

<td>100% N / cm²</td><td>200% N / cm²</td><td>300% N / cm²</td>

<td>Sample 1</td><td></td><td></td><td></td><td></td>

<td>SBR / CB</td><td>128.51</td><td>-</td><td>-</td><td>7.3</td>

<td>SBR / CB +3.5 TEPT *</td><td>692.59</td><td>-</td><td>-</td><td>7.2</td>

<td>Sample 2</td><td></td><td></td><td></td><td></td>

<td>SBR / CB + 3.5 TEPT</td><td>613.13</td><td>-</td><td>-</td><td>7.6</td>

<td>SBR / CB + 3.5 Antioxidants</td><td>87.60</td><td>-</td><td>-</td><td>7.2</td>

<td>Sample 3</td><td></td><td></td><td></td><td></td>

<td>SBR / CB</td><td>151.07</td><td>223.67</td><td>-</td><td>6.9</td>

<td>SBR / CB +1.5 TEPT, 2 PDCB **</td><td>435.56</td><td>1,255.68</td><td>-</td><td>7.1</td>

<td>Sample 4</td><td></td><td></td><td></td><td></td>

<td>SBR / CB + 3.5 Antioxidants</td><td>122.63</td><td>147.15</td><td>-</td><td>6.9</td>

<td>SBR / CB +1.5 TEPT, 2 PDCB</td><td>429.68</td><td>1,177.20</td><td>-</td><td>6.9</td>

<td>Sample 5 SBR / CB +1.5 TEPT 2 PDCB, 30 naphthenic oil ***</td><td>161.87</td><td>470.88</td><td>1,000.62</td><td>8.3</td>

<td>SBR / CB + 3.5 antioxidant, 30 aromatic oil ****</td><td>33.35</td><td>39.24</td><td>47.09</td><td>8.0</td>

<td>Sample 6 SBR / CB +1.5 TEPT, 2 PDCB, 20 naphthenic oil</td><td>216.80</td><td>751.45</td><td></td><td>10.1</td>

<td>SBR / CB + 3.5 antioxidant, 20 aromatic oil</td><td>46.89</td><td>58.66</td><td>-</td><td>10.1</td>

Nr.355295

Table IV (continued)

<td rowspan="2">test</td><td colspan="3">Modulus at stretch</td><td rowspan="2">Dose, Avg. megarads</td>

<td>100% N / cm²</td><td>200% N / cm²</td><td>300% N / cm²</td>

<td>Sample 7 SBR / CB +1.5 TEPT, 2 PDCB, 10 naphthenic oil</td><td>279.59</td><td>803.44</td><td>1,559.79</td><td>7.8</td>

<td>SBR / CB + 3) 5 Antioxidants, 10 aromatic oil</td><td>60.82</td><td>75.54</td><td>100.06</td><td>7.6</td>

<td>Sample 8 SBR / CB +1.5 TEPT, 2 PDCB, 20 naphthenic oil</td><td>223.67</td><td>712.21</td><td></td><td>9.6</td>

<td>SBR / CB + 3.5 antioxidant, 20 aromatic oil</td><td>38.26</td><td>38.26</td><td>-</td><td>3.5</td>

<td>Sample 9 SBR / CB + 20 naphthenic oil</td><td>97.12</td><td>207.97</td><td>484.61</td><td>9.9</td>

<td>SBR / CB + 20 aromatic oil</td><td>51,70</td><td>69.65</td><td>98,10</td><td>10.0</td>

<td>Sample 10 SBR / CB +3.5 TEPT</td><td>202.09</td><td>664.14</td><td>1,236.06</td><td>8.3</td>

<td>SBR / CB + 3.5 antioxidant, 20 aromatic oil</td><td>39.24</td><td>50.03</td><td>63.77</td><td>8.2</td>

* TEPT = thioether polythiol (Compound 2 in Table I) ** PDCB = p-dichlorobenzene *** Naphthenic oil = non-staining naphthenic softening and extending oil **** Aromatic oil = aromatic softening and extending oil

Antioxidants = N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine

These values ​​demonstrate the selective vulcanization of the rubber composition in a laminate when the rubber compositions are sensitized to radiation or desensitized. All samples were irradiated on both sides, with the exception of sample 6, which was irradiated on one side only, but this side received a higher dose.

Table V shows the use of the invention in a laminate strip in which the inner layer is vulcanized by radiation and the two outer layers remain unaffected. These laminates were made with three layers, each containing a solution styrene / butadiene copolymer as indicated in Table V. A polyethylene terephthalate film was placed between each layer to facilitate later separation. The laminates were subjected to a double-sided radiation treatment. Then the layers were separated and the physical properties determined for each layer.

Nr.355295

Table V

<td>Laminate A</td><td>(Mm)</td><td>dose (Megarads)</td><td>Module at 300% elongation (N / cm²)</td><td>Zugfestigkeit (N / cm²)</td><td>strain (%)</td>

<td>A) 100 SBR / 70 CB 40 aromatic 01/2 Antioxidants</td><td>0.53</td><td>3.8</td><td>28.25</td><td>35.22</td><td>800</td>

<td>B) 100 SBR / 50 CB / 2 PDCB</td><td>0.76</td><td>3.5</td><td>177.56</td><td>567.02</td><td>733</td>

<td>C) 100 SBR / 50 CB / 2 antioxidants</td><td>8.4</td><td>3.75</td><td>99.08</td><td>208.95</td><td>992</td>

<td>Laminate B A) 100 SBR / 70 CB / 2 antioxidants, 40 aromatic oil</td><td>0.58</td><td>5.7</td><td>46.11</td><td>73.58</td><td>840</td>

<td>B) 100 SBR / 50 CB / 2 PDCB</td><td>0.86</td><td>5.4</td><td>263.89</td><td>959.42</td><td>713</td>

<td>C) 100 SBR / 50 CB / 2 antioxidants</td><td>0.89</td><td>6</td><td>135.38</td><td>432.62</td><td>860</td>

Antioxidants = N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine

These values ​​illustrate the radiation vulcanization of the sensitized inner layer of a three layer laminate, the outer layers not being affected by the radiation treatment. The outer layers retain their tack while the inner layer is cured and retains its dimensions.

The doses taken by the layers in the above examples were measured by using strips of blue cellophane containing methylene blue as the dye. These strips were placed on top and bottom of the laminate to be irradiated. Before and after irradiation, the optical density on the strip was measured. The radiation causes the color to disappear, the degree of bleaching being proportional to the radiation dose absorbed by the strip.

The dose on the strip is determined from a graphical representation of the change in optical density (before and after irradiation) as a function of dose strength. The average dose on a slice is calculated from the surface dose and a predetermined curve of the depth dose distribution for the particular electron accelerator used. An even dose through each layer is achieved by choosing the right amount of electron energy and double-sided dosing technique.

The invention takes advantage of the fact that the greater the number of interfaces, the greater the resistance of the laminate to flow. The invention makes it possible to produce laminates which contain more layers and thinner layers than could hitherto be obtained. The interfaces distribute the expansion stresses more uniformly and give the laminate more dimensional stability.

- 13 No.355295

PATENT CLAIMS:

Laminate comprising at least two layers of rubber compositions, characterized in that at least one of the layers contains a sensitizer which upon crosslinking promotes cross-linking so that the layers are differently cross-linked after irradiation.

2. Laminate according to claim 1, characterized in that at least one of the sensitized layers has a different thickness over its cross section.

3. Laminate according to claim 1, characterized in that at least one of the layers contains a desensitizing agent which retards the crosslinking upon irradiation.

4. Laminate according to claim 3, characterized in that it contains at least three layers, wherein the two outer layers contain a desensitizing agent that retards the radiation crosslinking, and at least one of the inner layers contains a sensitizer which promotes cross-linking when irradiated.

A laminate according to claim 4, characterized in that the outer layers contain sulfur and sulfur vulcanization accelerators so that the outer layers cure when subjected to a heat treatment.

Laminate according to claim 1, characterized in that it has at least three layers, the inner layer containing a material which is degraded upon irradiation, and the outer layers adjacent to the inner layer contain sensitizing agents which promote cross-linking upon irradiation, so that the Laminate has a degraded inner layer between two at least partially crosslinked outer layers after irradiation.

7. Laminate according to claim 1 or 6, characterized in that it comprises at least three layers, wherein the inner layer contains a material which is degraded upon irradiation to form a liquid, and a material which is crosslinked upon irradiation, so that the Inner layer after irradiation has a trapped within a crosslinked material liquid.

8. A method for producing and crosslinking a laminate according to one of