DE2722351C3 - Pneumatic tire casing made from fluid polymers - Google Patents

Description

30th

The invention relates to a pneumatic tire casing which can be produced from fluid polymers according to the The preamble of claim 1, as known from DE-OS 21 40 949. J5

A general problem with pneumatic tire casings made up of several layers of different properties and exist without textile reinforcement inserts, lies in the relatively short service life of these pneumatic tire jackets, because they have poor flex fatigue strength. Under the weight of the vehicle, the Pneumatic tire casing constantly deformed. In the case of fabric-reinforced tires, the fabric reinforcement decreases at least 85% of the load. If the fabric reinforcement is omitted, it appears necessary to use a polymer with a higher Young's modulus to give the tire its shape maintains. However, harder polymers have a lower flexural fatigue strength. Enlarge small cracks with such polymers, especially on the side walls of a tire casing.

The invention is based on the object of providing a pneumatic tire casing of the type mentioned at the beginning create that has a longer duration.

This object is achieved by the characterizing features of claim 1.

A preferred embodiment of the invention is specified in claim 2.

The advantages that can be achieved by the invention are in particular that the inventive f> o Pneumatic tire casing can be produced by the rotational molding process.

Embodiments of the invention are explained below with reference to the drawing. It shows

Fig. 1 is a partial perspective view of a pneumatic tire ^;

F i g. Figure 2 is a partial cross-sectional view of the laminated tire of Figure 1, wherein

part of the sidewall of the tire is shown,

F i g. 3, 4 and 5 partial views similar to that of FIG. 2, showing other embodiments of the laminated tire, and FIG

F i g. 6 is a partially schematic cross-sectional view of an embodiment of a device for Manufacture of the laminated pneumatic tires.

In Fig. 1, a pneumatic tire casing 10 is shown, which has a tread or profile part 12 and two Side wall parts 14 comprises which have no fabric or textile reinforcement. In the tread part 12 reinforcement tapes may be included. Although the tire is generally annular in cross-section the present invention can also be applied to tires having a special section will.

The tire casing 10 is made from a number of plies of polymeric material. Each ply is generally of uniform thickness and completely covers the adjacent ply. In the case of the in FIG. In the embodiment illustrated in FIG. 2, the tread portion and each of the side wall portions 14 comprises a thirteen-ply laminate made up of alternating plies Hund L of high and low modulus. The low modulus ply L is provided on both the inside surface and the outside surface of the tire and each other ply includes a high modulus ply H. This particular configuration enables the manufacture of a tire with the desired strength and rigidity using layers H nut high modulus at the same time the inclination is minimized to flex cracking. Although thirteen layers are often preferred, a different number of layers will also give good results.

3 shows a further embodiment, likewise with thirteen layers, a layer M with a medium module being provided in addition to the layers H with a high module and the layers L with a low module. This arrangement is similar to that in FIG. 2, ie the layers H and L alternate regularly with the layer L with a low modulus on the inner and outer surface of the tire. However, there is a middle module layer between each layer L and the next layer //. This means that layers H with an extremely high modulus can be used without a sudden change in module when changing from layer H to layer L. If the tire includes a large number of plies, such as 25 to 50 or more, it may be desirable to have more than one ply with an intermediate module between the low modulus ply and the high modulus ply.

In Fig. 4 shows a further embodiment, the layers L and // with low and high modulus, respectively, as in FIG. 2 alternate in the inner part of the laminate and wherein several of the outer layers are formed from the same low modulus material. In this figure, the first three plies on the inside and outside of the carcass part are low modulus plies. An advantage of this construction is that the inner and outer surface portions of the tires are subject to greater bending stresses which are better withstood by low modulus material.

F i g. 5 shows a further embodiment, the different layers having different thicknesses. Both the F i g. The embodiments shown in FIGS. 2, 3 and 4 all have the same thickness. However, this can

also vary and the layers can be of different thicknesses. It is often desirable. Produce layers L with low modulus that are slightly thicker than layers H with high modulus. In the case of the in FIG. 5, the layers L and H with low and high modulus alternate regularly as in FIG. 2, except that two layers L with low modulus are provided on the inner surface.

Different methods can be used to produce the tire casing according to the invention will. The non-vulcanized or non-hardened pneumatic tire casing can be built, for example, by making a cylindrical laminate with ten or more layers and then the laminate expanded from cylindrical to annular shape by a process similar to that of an known flat belt or flat drum processes. The tire casing can also be made, by applying the plies to the laminate while the laminate has an annular shape or a has another desired cross-section, as will be explained in more detail.

Some of the first of the pneumatic tire casings of the present invention were made manually by clicking on the The outer surface of a metal mold has a series of layers of liquid polymeric material with moderately uniform density applied. Another possible method of building the tire casing is in that one successive layers of unvulcanized Rubber or rubber as sheets or foils or plate material or similar material brings up. To reduce costs, it is useful to use a liquid polymeric material and to use automated procedures.

The polymeric materials that can be used for the tire casing are elastomers, elastoplastic materials, or plastics or plastic materials with a high modulus. The softer layers L with a low modulus of the tire are produced from elastomers and / or elastoplastic materials and the harder layers H with a high modulus are preferably produced from elastoplastic materials or plastic materials with a high modulus or plastic materials with a high modulus.

The elastomers are characterized by a main glass transition temperature below about 20 ° C., a Young's modulus in the range from 70 to 4200 n / cm ² and the ability to withstand elongations of 100% or more without permanent deformation or tearing. Suitable elastomers are, for example, polyurethane rubber, natural rubber, polybutadiene and various other synthetic rubbers including SBR rubbers.

The elastoplastic polymer materials can have Young's moduli in the range from 2100 to 35,000 N / cm ² . At room temperature, these materials normally show flow limits or flow points below 50% elongation and breaking strengths above 2800 N / cm ² and elongations at break which are above 100%. These materials are usually characterized by the fact that they are multiphase, because vitreous or crystalline structures are usually detectable in certain areas. Typical materials in this group are block polymers such as styrene-butadiene-styrene triblock polymers, polyester block polymers, segmented polyurethane polymers and isomers.

The diastic materials or plastic materials

with a high modulus are characterized by Young's moduli of 35,000 N / cm ² or higher and flow limits or flow points and / or failure points when elongated below about 15%. They have main glass or melt transition temperatures above 100 ° C. Suitable materials of this group are compositions of polyamides, polycarbonates, epoxy resins and polystyrenes.

The elastomeric materials used in the layers L low modulus should have a major glass transition temperature below about -20 ⁰ C and may contain groups that can form covalent crosslinks. The molecular weight of the chains between the covalent crosslinks is preferably about 5,000 to 40,000 and more preferably about 8,000 to 20,000.

In general, the polymeric material for the various layers of the tire casing should have a calculated molecular weight of at least 10,000 and a Shore A durometer hardness of at least 20 and preferably have a tensile strength of at least 700 N / cm ² . The softer layers L with a low modulus have an elongation of normally at least 30% and preferably at least 50% and a Shore A durometer hardness of at least 30 and preferably not more than 90. The polymeric material of the softer layer L with a low modulus preferably has a tensile strength of at least 1400 N / cm ² .

As will be shown below, there is a general one between the Shore hardness and the Young's modulus Relationship.

Shore hardness
(BS. & 1.RH)

Young module
N / cm ²

30th
50

75

91
210
940

The Shore hardness and Young's modulus values listed in the present application should be in generally obey this relationship.

The vulcanized or hardened layers L with a low modulus of the tire preferably have Young's moduli in the range from 210 to 3500 N / cm ² and normally in the range from 350 to 2100. The preferred hardness depends on the thickness of the various layers, their arrangement, the stiffness of the harder layers and other factors.

The hardened or vulcanized layers H with a high modulus have Young's moduli in the range from 2000 to 70,000 N / cm ^2, which are normally at least twice the moduli of the adjacent layers L with a low modulus. The modulus is preferably in the range from approximately 3500 to 35,000 N / cm ² .

The ratio of the Young's modulus of each hard ply // of the laminated tire to the Young's modulus of each soft ply L can be up to 300: i, but is generally in the range of 3: 1 to 20: 1 at one Car pneumatic tire casing.

The appropriate modulus for the harder plies, H , of course, depends on many factors and should be selected to provide a composite tire with the desired overall modulus and stiffness. For example, if the laminated tread portion of the tire is 50% by weight

polymeric material with high modulus and 50% by weight of material with low modulus then the Young's modulus can be 350 to 1400 n / cm ² for the soft layers L and 2800 to 5600 N / cm ² for the hard layers H. On the other hand, if the amount of high modulus material is reduced to only 25% by weight, then the Young's modulus can be increased to 7,000-10,500 N / cm ² or even 14,100 N / cm ² .

In general, the weight of the low modulus layers L should be at least equal to the total weight of the high modulus layers H as illustrated in the accompanying drawings. It is expedient to provide layers L with a low modulus on the inner and outer surfaces of the laminate, in particular on the outer surfaces of the side wall parts.

The number of layers can be limited in order to reduce manufacturing costs. However, it is preferably to use at least 7 layers, and more preferably at least 9 layers. The number of layers can vary from 5 to 1000 depending on the thickness of each layer. Each ply can be from 0.00254 to 0.254 cm thick be. The number of layers is preferably in the range from 7 to 100, the thickness of the layers in the range from 0.0127 to 0.127 cm. Each layer is preferably of the same thickness. Each location is preferred in theirs Circumference continuous and without openings, although this is not essential. The locations can may be deformed during the manufacture of the tire, for example if the tire after the Formation of the laminate is molded and before it is fully vulcanized, etc. is hardened.

By varying the number of plies, their thickness, the arrangement of the plies and the hardness of the polymers used, one can produce an unlimited number of different laminated pneumatic tire casings. The simpler arrangements in which each low modulus layer L has the same hardness and each high modulus H layer has the same hardness are generally preferred. In order to improve the adhesion between the layers, it is desirable to produce all the layers from the same polymer (for example polyurethane). However, the adhesion problems can be resolved using adhesives or perforations in the layers or in some other way.

Good results are obtained when all layers H having a high modulus of the same elastic material with an elongation to break of about 5 to about 10%, and a Young's modulus of 3500 bi ^c 14100 N / cm ² are prepared, and when all of the layers L with a low modulus can be made from the same elastomeric material with an elongation of at least 5 ° / o and a Young's modulus of 350 to 1410 N / cm ² . The tensile strength of the layers with high modulus should be at least 1410 N / cm ² and preferably at least 2110 N / cm ² .

In a particular laminate of this type, shown in FIG. 3, layers L should have a Young's modulus of 210 to 700 N / cm ^2, layers My Young's modulus of 700 to 2110 N / cm ^2, and layers H should have a Young's modulus of 7000 to 35200 N / cm ² own.

The tire jackets can be made from vulcanizable or hardenable sheets or tires in different ways. Sheets or foils made of rubber or plastic or made of flowable polymeric materials such as through Die casting or extrusion. A flowable, hardenable or vulcanizable polymeric material with a viscose

did at processing temperatures that will allow the material to flow under its own weight in a reasonable time. The material for the LmW low modulus layers should be a material which can be cured or vulcanized in a reasonable time and which gives a tensile strength which is preferably at least 700 N / cm ² .

The polymeric material is a fluid polymer, such as a polyurethane that can be cured or vulcanized quickly and that in an automated way Device can be processed. The viscosity of the polymeric material can be determined by the use of solvents or plasticizers or by the use of heat or by suitable selection the hardening or vulcanizing agent, by changing the hardening or vulcanizing temperature or on other types can be set. A large number of different polymers, as detailed below explained can be used.

The layers can be formed by spraying or otherwise applying curable liquid polymeric materials on the inside of the tire mold. This can be done with or without a squeegee for deforming the Layers take place.

In Fig. 6, there is shown, partially schematically, a mold 20 which can be used to make a laminated pneumatic tire casing. It receives a left mold half 22L and a right mold half 22Λ The mold halves are attached to flat circular retaining plates 2AL and 24R , which are attached to bearing blocks 26A. or 26R are attached. This arrangement enables the assembly of mold halves, plates and bearing blocks to be freely rotatable about the hollow shaft 30 which rests on ball bearings 28. A pair of spray tubes 32 and 34 are mounted within the shaft 30 so that the liquid polymer can be dispensed into the mold. The polymer is applied to the inside of the mold cavity from the spray nozzles at the end of tubes 32 and 34. The ends of tubes 32 and 34 are firmly held in place by an annular support member 36 mounted on shaft 30. Ball bearings 38 are mounted around the periphery of member 36 at its opposite ends so that a rotatable support is provided for mold halves 22L and 22R so that they can rotate freely with respect to the shaft. The shaft 30 and the support element 36 can be arranged stationary or they can optionally be mounted so that they can rotate.

The inner surface of the mold 20, which is defined by the two mold halves 22Z. and 22R , may be such that the air duct, including both the tread portion and the sidewall portions, can be made entirely in the mold 20. However, the mold 20 may be such and used to form only the laminated sub-structure to which the tread portion is applied after it is removed from the mold. Various methods can be used in this case to apply the tread portion. If necessary, reinforcement bands or belts or belts can be provided under the running surface.

In the form shown in Figure 6, the Spray nozzle or the spray nozzles can be designed so that a spray of liquid polymer on the radially outer (running surface) surface and optionally on the inner surface of the mold is as indicated by the dashed lines

extending radially from the end of tube 34 in FIG. In other words, they can Spray nozzles dispense the liquid polymer so that a layer of substantially uniform thickness is formed covering the entire inner surface of the mold.

In forming the tire casing, it is generally preferred to use alternating layers L and H of polymeric materials of low modulus and high modulus, respectively. In the mold 20 shown, two spray tubes 32 and 34 are provided for the two different polymeric materials. If three different polymer materials are to be used, then three spray nozzles must be provided. The high modulus polymer is fed through spray tube 34 while flow through tube 32 is shut off. The low modulus polymer is introduced through spray tube 32 while tube 34 is shut down. By alternately supplying the polymers through different pipes, alternating layers can be formed on the tire.

Assuming that the mold 20 is rotating continuously and not stopped periodically, one layer becomes made of polymers! Material is formed on the inside surface of the mold by drawing from one of the spray tubes 32 or 34 sprays during one or more revolutions of the mold with respect to the spray nozzle. Subsequent the other layer can be formed in a similar manner during one or more revolutions by spraying the polymeric material from the other spray tube. The centrifugal force of the Rotation of the shape can aid in the formation of the location. Various rotational molding processes can be used use. It should be used curable or vulcanizable polymeric materials that quickly cure or vulcanize enough so that one layer retains its shape while the next Location is applied. A fast-curing or fast-vulcanizing material is also useful thus ensuring that the layers are formed of uniform thickness, with the shape is maintained while the shape is rotating.

The sequence of the processes or process steps depends to a certain extent on the hardening or Vulcanization rate and the speed from, with which the liquid polymeric material is fed. For example, the shape can be slow can be rotated and the polymeric material can be fed from a flush pipe at such speed that the desired circular position is formed during one revolution of the mold. That Process can also be varied so that several revolutions of the mold are made during formation one location are required. In some cases it can It may be necessary to continue the mold for one or two revolutions after a circumferential layer has been formed to rotate so that there is substantial curing or vulcanization prior to spraying the next layer is achieved. If the curing or vulcanization rate is fast enough, you can spray the subsequent layer within half a turn after applying the previous layer was going to begin.

The term "partially hardening" or "partially vulcanizing" means that the material is sufficient has been stiff or is sufficiently set so that it is reasonably dimensionally stable so that the following

lowing layer can be applied. This term does not necessarily include a real one Hardness.ι or vulcanization of the material.

It can, using the forms of the general kind illustrated in Fig. 6, various fluid polymeric materials can be used. The viscosity or flowability of the liquid Polymers can be made by using heat, solvents, or plasticizers other processes can be controlled so that movement of the liquid material to the Mold surface becomes possible at a suitable rate.

Various fluid polymer materials can be used in carrying out the method according to the invention including monomers, melts, prepolymers and solutions can be used. The fluid polymeric materials must be liquid at the time of processing and they must with the Processing temperatures have such a viscosity that they are under their own weight in a flow for an acceptable period of time.

One of the preferred polymers for practicing the present invention is a polyurethane. Such a polymer is usually made by reacting from 0.95 to 1.2 equivalent weights of one organic polyisocyanate with 2 to 3 functional isocyanate groups with one equivalent of an organic Compound with a molecular weight of at least 1000, which contains active hydrogen atoms, reactive with isocyanate (—NCO-) groups. In many cases you can get an organic one Use chain extenders that have hydroxyl groups, amino groups, carboxyl groups or others Contains groups with active hydrogen atoms that react with isocyanate groups.

The organic compounds with active hydrogen atoms that react with - NCO groups are For example, polyesters containing terminal hydroxyl groups, polyester amides, polyhydric polyalkyl ethers, polyhydric polythioethers, polyacetals and similar compounds.

The organic polyisocyanates used in the manufacture of the polyurethanes can be various Species include aliphatic, aromatic, alicyclic, and heterocyclic species, such as them in US Patent 32 08 500 are described. Generally they contain at least 8 carbon atoms. Excellent results are obtained using aromatic diisocyanates such as toluene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI) or other diphenylalkane diisocyanates or the like Connections, received. For example, the organic diisocyanates can be an 8: 20 or 65:35 mixture be made from 2,4- and 2,6-toluene diisocyanate.

Suitable diisocyanates generally contain 8 to 20 carbon atoms and include the various Toluene diisocyanates, the various naphthalene diisocyanates, the various phenylene diisocyanates and the various diphenylalkane diisocyanates such as they are described in US Pat. No. 3,701,374, the entire contents of that specification The disclosure for the present application should also apply. Suitable diisocyanates are, for example

33'-dimethyl-4,4'-diphenylmethane diisocyanate
33'-dimethyl-4,4'-biphenyl diisocyanate,
3,3'-dimethoxy-4,4 ^r -biphenyl diisocyanate
and the same.

Mixtures of the various diisocyanates mentioned above can also be used.

Polyurethanes with the desired molecular weight can be made in different ways will. In general, it is intended to use bifunctional reactants, the flexible linear ones Polymers result. For example, it can be a polyhydric alcohol or a terminal hydroxyl group containing polyether or polyester with an organic diisocyanate to form a liquid Prepolymers having a molecular weight of 800 to 20,000 with essentially either only hydroxyl end groups or only isocyanate groups can be produced and then the prepolymer can be made using of diamines, diols or diisocyanates depending on the terminal or end group in the Prepolymers are cured or vulcanized. The most suitable polyurethanes are those that Implementation or masking of the hydroxyl groups of polyalkylene glycols with a molecular weight of 800 to 20,000 with diisocyanates to form prepolymers and then chain extension and Hardening or vulcanization of the prepolymers by means of a diamine or diol hardener such as MOCA or an alkylene glycol.

The terminal hydroxyl-containing polyester used to form the polyurethanes can be reaction products of a polycarboxylic acid and a polyhydric alcohol as described in the aforementioned LJS patent specification 32 08 500. As alcohol you can for example Use ethylene glycol or propylene glycol.

The organic compound containing active hydrogen atoms for reaction with the isocyanate groups can also be a polyhydric polythioether or a polyester amide, as it is in the cited US Patent 32 08 500 is described. A polyhydric polyalkylene ether is useful. The ether can for example be the condensation product of an alkylene oxide with a glycol, such as ethylene glycol, Propylene glycol, butylene glycol, or a similar glycol. Any suitable alkylene oxide condensate can be used use, such as condensates made of ethylene oxide, propylene oxide, butylene oxide, Amylene oxide, styrene oxide and their mixtures.

In the preparation of the liquid prepolymers, the organic diisocyanate (b (preferably MDI or TDI) with polyalkylene glycols with molecular weights in the range from 800 to 20,000, especially poly (alkylene glycols) with alkylene groups having 2 to 10 carbon atoms, such as

Poly (ethylene glycol),

Poly (propylene glycol),

Poly (trimethylene glycol),

Poly (tetramethylene glycol),

Poly (hexamethylene glycol),

Copolymers of such high molecular weight glycols

and mixtures of the above poly (alkylene glycols) are reacted.

The prepolymers generally have terminal isocyanate groups and they can with various Diamines are hardened. The diamines come with an organic group in the middle with 2 to 20 Carbon atoms that are attached to two amino groups, such as

Ethylenediamine,

Tetramethylenediamine,

Hexamethylenediamine,

p-phenylenediamine,

Methylene-bis-2-chloroaniline (»MOCA«),

4,4'-methylene-bis-aniline,

3,3'-dichloro-4,4'-diaminodiphenylmethane,

Benzidine,

3,3'-dimethylbenzidine,

3,3'-dimethoxybenzidine,

3,3'-dichlorobenzidine,

4,4'-diaminodiphenylmethane and

Cumoldiamine.

In these polyurethane rubbers, the chains from the hardened polymer contain the repetitive grouping

-4P-O-CO-NH-R ₁ -NH-CO-NH-R ₂ -NH-CO-NH-R ₁ -NH-CO-Ot-

where P is a poly (alkylene ether) chain with a high molecular weight, R _{1 is} the organic group of the diisocyanate and R2 is the organic middle group of the diamine. This type of polymer, having the appropriate molecular weight, gives excellent results when the polymer is used to make high and low modulus plies L and H of tire laminac. The hardness and modulus of these polyurethane polymers can be increased, for example, by increasing the isocyanate and glycol or diamine content of the system

The polyurethane will depend on the type of manufacturing process used. The polyurethane that is best for spraying, it cannot for film extrusion or any other process Best seia

The liquid, commercially available polyurethane rubbers can be used. For example are made with Adiprene-L-100 prepolymers (4.1% NCO), Adiprene-L-167 prepolymers (63% NCO) and Adiprene-L-315 prepolymers (9.5% NCO) manufactured by E.I. du Pont de Nemours & Co, good results obtain. These liquid prepolymers can be mixed with known diamines such as MOCA, Caytur 7 or Caytur 21 (4,4'-methylene-bis-aniline), using an equivalent weight ratio of diamine to prepolymer cured from about 0.95 to about 1.10. Caytur 7 is a eutectic mixture of m-phenylene and cumoldiamine.

sn polyurethane prepolymers, such as Adiprene-L prepolymers, can, for example, from TDI and a Poiyaikyiengiycoi or Poiyoi, such as Poiy (tetramethyienätherdiol), getting produced. Similar prepolymers can be made using MDI instead of TDI or using a slightly different polyol. Various poly (alkylene glycols) and poly (alkylene ether) polyols can be used both diols and triols; the prepolymers can either have terminal - OH groups or Terminal - contain NCO groups (they preferably contain the latter).

The polymeric material used can also be a polyamide plastic such as nylon 66, nylon 610 or Nylon 6. Various long chain synthetic polymeric amides, the repeating amide types Contained as an integral part of the main polymer chain, such as those made by Condensation of diamines and dibasic acids,

Il

those produced by condensation of polycarboxylic acids with polyamides, or those produced by polycondensation made by caprolactam.

Various triamines can be used such as diethylenetriamine and the like. However, it is prefers to use diamines. Suitable diamines are, for example, ethylenediamine and diethylenediamine. Pentamethylene diamine, hexamethylene diamine, phenylene diamine and the like or their mixtures.

Various polybasic acids in the range from succinic acid to Sebacic acid and including, for example, succinic acid, aconic acid, adipic acid, malic acid, Itaconic acid, fumaric acid and similar acids can be used.

The polyamides useful in rubber tires made in accordance with the present invention are disclosed in U.S. Patent 32 08 500 described, to which reference is expressly made. Preferred polyamides are those made from diamines and dibasic acids, such as the reaction products from Hexamethylene diamine or a similar diamine with a dibasic acid such as adipic acid or sebacic acid.

Although there are many different types of polymers that can be used here are the promising polymers the polyurethanes and polyamides or nylon compounds like them generally described in US Pat. No. 3,2.08,500. Right now, the polymers are the most promising are the polyurethanes, especially polyether urethanes and polyester methanes.

It is an advantage of the polyurethanes that they can be obtained in liquid form with viscosities that are suitable for Spray and are united for spreading. Furthermore, they can both be high in the vineyards Modulus as well as in the layers of low modulus can be used, causing adhesion or sticking problems be avoided. You can also use polyurethanes with different molecular weights mix to produce mixtures with the desired properties.

For example, the laminated tire of the present invention can be made using Adiprene L-42 (molecular weight about 3000) for the low modulus layers and Adiprene L-167 (molecular weight about 1330) for the layers with high modulus. The layers with high modulus can also using a mixture of 60% by weight of Adiprene L-167 and 40 parts by weight of Adiprene L-315 (Molecular weight about 900). The hardening agent soiite MöCA, Caytur 2i or ein other suitable diamine. If a plasticizer is used, one can use dioctyl phthalate or use a similar connection. The hardening agent should allow for relatively rapid hardening, so that the time that passes after each layer is applied and before the next layer can be applied, is kept as short as possible.

The polyurethane prepolymers can also be modified in various ways so that the For example, Adiprene L-167 (a prepolymer with a Brookfield viscosity from about 5000 to about 7000 centipoises at 30 ° C and about 250 to about 350 centipoises at 100 ° C) with 1,4-butanediol and trimethylolpropane in suitable Conditions are cured to obtain a rubber layer of the desired type

curable polyurethane:; composition should for example be prepared by adding 160 parts by weight of Adiprene L-167 with about 9 parts of 1,4-butanediol, about 1.6 Parts of trimethylol propane and a small amount of dioctyl phthalate mixed.

The tire manlei according to the invention is preferably constructed so that the tensile strength of the laminate (gap test method) is 120 to 1800N or more per straight 2.54 cm, and so that the layers with low modulus have a tensile strength of at least 700 N / cm ² a Shore A durometer in the range of about 30 to 90 and an elongation of at least 50% (more preferably at least 100%).

The curable polymers used here do not have to be liquid. However, liquid polymers make it easier to manufacture. The viscosity of the liquid polymers may be for example 1000 to 50,000 centipoises, and they should be less than 100, 000 centpoises at 30 ⁰ C. The viscosity can be prepared by adding appropriate amounts, sometimes up to 10 or 20 parts of a plasticizer such as dioctyl phthalate per 100 parts by weight of the polymer can be adjusted.

In some cases, solvents can be used with the polymers so that the desired flowability is obtained. The choice of solvent depends on the type of polymer and the Type of curing system. Various solvents can be used including ethyl acetate, Acetone, toluene, methyl ethyl ketone, xylene, /? - ethoxy ethyl acetate and the like. They should be clean and free from moisture.

Although different polymer formulations are used in the laminates of the tire casings in the L plies with low modulus and in the plies H with high modulus, similar preparations can also be used in all plies for laminates with improved flex tear resistance and the tensile moduli in a given direction, such as a circumferential or radial direction, etc., are significantly different from the neighboring layers. The difference in tensile modulus between adjacent layers H and L (e.g. Fig. 2) can be achieved when the same polymer is used in both layers, as a result of different molecular orientations in the adjacent layers.

The term "tensile modulus" in the present application means the tension in N / cm ² that must be exerted on a specimen in order to stretch it to the specified elongation, such as 10%, 100% or 200%.

In a pneumatic tire casing according to the invention (for example according to FIG. 2), each layer has a 10% modulus in one direction which corresponds to at least approximately twice the 10% modulus of the next adjacent layer in this direction. For example, the desired difference in tensile modulus between layers H and layers L in different embodiments of FIGS. 2 to 5 can be achieved by molecular orientation or by using different polymers in different layers or by both measures.

The use of the same polymer or similar polymer in adjacent layers is advantageous, as this achieves good adhesion.

In the present application, the term "parts" means parts by weight and the term "Polymers" includes homopolymers or copolymers unless otherwise specified.

The term "fluid" in connection with a

polymeric material indicates that the material has a viscosity such that it can flow during processing. The viscosity can be, for example, from 100 to 10,000 centipois.es at 30 ⁼ C and they

shouldn't 100,000 centipoises at this temperature exceed.

The following example illustrates the invention.

example

! in this example! is the inventionP «. Manufacture of tires explained that have a much improved resistance to distribution of cut cracks or which hardly form cracks. Laminated ones are used to explain these properties and homogeneous samples subjected to the De Mattia bending test. A comparison is made between each laminated sample and a homogeneous sample made from a mixture of the materials in the particular Laminate and was made in the same proportions. The leather of the samples was 2.54 cm wide. 0.635 cm thick and 6 inches long. The samples are cured in a press for 2 hours at 121 ° C. and then in one Oven post-cured or post-vulcanized at 80 ° C for a further 2 hours. Each sample is then given an artificial crack 0.254 cm along the 0.6354 cm wide surface, perpendicular to the 2.54 cm wide surface is attached. Fatigue test is carried out on a De-M attia bending machine where the samples (333 cycles per minute and at room temperature) and where the applied crack is longitudinally laterally the width of the specimen propagates.

In this experiment two different materials from two preparations are used, which are used as "100" and "167" are designated as follows ("parts" mean parts by weight).

component Parts "167" "100" _ Adiprene L-IOO (I) * 100 100 Adiprene L-167 (2) * - 0.1 DC-203 (3) * 0.1 - Dioctyl phthalate plasticizers 10.0 31.1 Caytui 2 i (4) * 20.3

130.4

131.2

Footnotes: *

(1) and (2) are liquid prepolymers as described above became. (3) is a liquid silicone molding and emulsifying agent. Dow Corning; Uiid (4) is a 50% Dispersion of methylenedianiline / sodium chloride complex in dioctyl phthalate. Du Pont.

Samples are made from each of these preparations alone and the De Mattia test becomes to determine the number of cycles required for the 0.254 cm long crack to be 1.27 cm

Table 1

becomes long. The values of the module are given in units of 10 ⁶ Pascal. The following other properties are also determined:

properties

"100"

"167"

10% module 1.1030 2.5507 100% module 2.7920 4.7568 200% modulus 3.5159 5.9288 Tensile strength (break) 14,167 15.787 Elongation (break) 750% 575% hardness Shore A 83 91 Shore D 29 42 De Mattia (cycles up to one 500 1000 Crack of 1.27 cm)

Preparations "100" and "167" are then used to prepare samples containing both materials used. For the mixtures, the ratio listed in Table II means the ratio of "100" to "167" and for the laminates listed in Table II a layer more of "100" than of "167" is available, with both outer layers being the "100" layer.

15th 2: 1 27 22 351 7 layers 16 9 layers 5: 4 in 10 ^(l Table II 3 layers 1.965 1.413 4: 3 1,379 1.724 properties 3.516 5 layers 3: 2 2,895 2.964 3.171 1.55 16.68 Pa ^c cai 7.652 1.551 11.03 15.10 10% module 3.206 730% 1.275 2.034 470% 2,999 575% 720% 100% module 12.68 2.585 3,654 13.37 Tensile strength (break) 660% 86 6.825 13.17 - 650% - 86 Elongation (break) 33 445% 565% - - 34 hardness - 1600 6000 84 5200 1400 Shore A - - 87 32 Shore D 1500 - 32 1750 De Mattia (cycles up to 5000 1000

to a crack of 1.27 cm)

In Table II, the heading "3 layers" in the second column means one laminated sample, the two Contains outer layers of "100" and a message from "167". The next column "2: 1" means one homogeneous sample made from a mixture of 2 parts by weight "100" and 1 part by weight "167" was produced. The following column means laminated and homogeneous samples with different ones Circumstances. For example, the 91-ply laminated sample can be compared with a homogeneous sample made from a 5: 4 mixture as indicated in the last column. jo

The above values show that a remarkable increase in fatigue life, as from 400 to 500%, is obtained with a laminated sample, which at the same time has the physical Retains properties that they have in the conditions to be expected in a pneumatic tire casing got to. Although the values for tensile strength and elongation are somewhat irregular, this is only what happens Voltages well above those observed in end-use, and does not detract from the fact that a great improvement is observed in fatigue strength. That something irregular behavior in terms of tensile strength and elongation at break values in these samples Relation to the cracks in the specimens, which influence these properties but not the bending behavior

For this purpose 2 blue drawings

Claims (2)

Patent claims: 1. Pneumatic tire casing which can be produced from fluid polymers and has a tread and a flexible one Sidewalls made up of several rows of layers of different properties, the layers have no textile reinforcement and the polymer has a molecular weight of at least 10,000 and has a Shore A durometer hardness of at least 20, characterized in that that the difference in properties is that the vulcanized or hardened polymer of one row of layers (L) has a Young's modulus of 70 to 3500 N / cm ² and the vulcanized or hardened polymer of the other rows (H) has a Young - has a modulus of 2000 to 70,000 N / cm ² ,
that the Young's modulus of the vulcanized or hardened polymer of the layer (H) is three to twenty times the Young's modulus of the vulcanized or hardened polymer of the layer ^ !, 'and that the layers (L) and the layers (H) are arranged alternately. 2. Pneumatic tire casing according to claim 1, characterized in that the side walls each from 9 to 100 There are layers approximately 0.00254 to 0.254 cm thick.