Field of the Invention

The present invention relates to a polyamide 56 based reinforcement cords for elastomeric articles, in particular for tires. The rubber reinforcing cords comprising of polyamide 56 yarn characterized in that said polyamide 56 yarn is at least partially biobased.

Background

In order to give full play to the durability of the tire, it is necessary to use various reinforcing materials to reinforce the strength or rigidity. In the tire, fibers are incorporated into the rubber matrix serving as a skeleton component to stand the large scale of load and maintain its shape, which have a great influence on the physical and mechanical properties of the entire composites. The cap ply of tire serves as an intermediary between the steel and tread rubber, and cords referred to as cap ply fulfill the role of improving adhesion and preventing peeling when running at high speeds. In addition, it also functions to inhibit deformation by firming up tires that have expanded at high speeds and high temperatures.

Cords using polyamide 66 fibers are currently used nearly exclusively for cap ply cords. This is because polyamide 66 fibers have superior rubber adhesion properties required for use as cap ply cords and demonstrate tire-firming effects attributable to thermal contraction, while also demonstrating a favorable balance between strength and heat resistance and the like. However, tires using polyamide 66 fibers for the cap ply are susceptible to the occurrence of deformations referred to as flat spots caused by sudden temperature changes attributable to driving or parking, while also having problems with respect to increased rolling resistance and straight running stability.

Examples of fibers used in tire cords made of materials other than polyamide 66 include those made of polyethylene terephthalate (PET), polyethylene naphthalate (PEN) and aramid or hybrid cords which made from their yarns. In general polyethylene terephthalate (PET) fibers highly elastic and have low shrinkage. High modulus low shrinkage (HMLS) fibers are superior to polyamide 66 in modulus and shape stability. However, fibers made of PET or PEN have poor rubber adhesion properties, require two rounds of adhesive coating treatment while polyamide 66 fibers only require one round, and tend to result in increased processing costs and increased costs attributable to equipment restrictions. Aramid fibers also have poor rubber adhesion properties, required two rounds of adhesive coating treatment and have the problem of increased costs.

These textile reinforcements based primarily (directly) on fossil raw materials. On the other hand, the recent world automobile market is devoted to environmentally friendly technologies, that is, in order to cope with environmental problems, efforts have been made to find sustainable solutions. With this pace, the tire market also strives to utilize environmentally friendly reinforcement materials in tire. It is known to use non-petroleum-based textile reinforcements in tire made of viscose, such as rayon or lyocell. The disadvantage of natural fibers, that is, of non-petroleum-based materials as material for textile reinforcements, is that they do not have an endless fiber structure and a strongly fluctuating fiber quality. In addition, the lack of shrinkage makes the special use of rayon as a reinforcement in the belt bandage more difficult. Another disadvantage of rayon is that rayon is sensitive to moisture and the breaking strength of the reinforcement is reduced by moisture absorption. In addition, rayon is expensive to purchase.

The trend is towards developing and using environmentally friendly raw materials which are derived from biomass without having to accept any loss in the durability of the products made from them. The present invention is based on the object of providing a reinforcement and a reinforcement layer - comprising at least one reinforcement - for elastomeric products, in particular for a tire, which consists of environmentally friendly and resource-saving materials and can be produced sustainably at the same time. In addition, the reinforcement cord should have a consistent product quality.

Summary of the Invention

A first object of the invention may be to provide environmentally friendly reinforcement cords which are comparable with conventional polyamide 66 reinforcement cords for tire applications.

Another object of the invention may be to provide a hybrid reinforcement cords comprising of polyamide 56 yarn characterized in that said polyamide 56 yarn is at least partially bio-based. Another object of the invention may be to provide a pneumatic vehicle tyre characterized in that it includes environmentally friendly reinforcement cords comprising of polyamide 56 yarn characterized in that said polyamide 56 yarn is at least partially bio-based.

Another object of the invention may be to provide an aircraft tyre characterized in that it includes environmentally friendly reinforcement cords comprising of polyamide 56 yarn characterized in that said polyamide 56 yarn is at least partially biobased.

Another object of the invention may be to provide a radial passenger car or light truck tyre characterized in that it includes environmentally friendly reinforcement cords comprising of polyamide 56 yarn characterized in that said polyamide 56 yarn is at least partially bio-based.

The present invention is defined by the scope of claim 1. Further preferred embodiments are defined by the dependent claims or the description hereinbelow.

Detailed Description of the Embodiments

Polyamide 56 based reinforcement cords for elastomeric articles to fulfill the objectives of the present invention is illustrated in the accompanying figures, in which:

Figure 1: A view of hybrid cord consisting of PA56 and PA66 plies

Figure 2: A view of reinforcement cord is characterized in that it contains at least one ply polyamide 56, and further ply consisting of other polymers (PA66, rPA66, etc..)

Figure 3: A view of the reinforcement fabric with parallel cords in which polyamide 6.6 and polyamide 5.6 cords are arranged sequentially (alternately) in said reinforcement fabric

Figure 4: A view of fabric consisting of the paired cords. Within each paired cord, one cord is PA66 and the other is PA56.

Figure 5: A view fabric consisting of the paired hybrid cords. Each hybrid cord within the pair is consisted of PA66 and PA56 plies.

The object is achieved in that the reinforcement comprises fibers made of biobased polyamide 56 polymers. From the patent application CN110373736 A, polyamide 56 fibers are known in the literature. In this case is disclosed, the product are affected by the material composition of the reinforcement cord derived from polyamide 56 polymers.

In this way a conventional polyamide 56 reinforcement cord which is made of bio-based polyamide 56 polymers, can be replaced. Depending on the specification of the final product of this reinforcement cord is suitable to use as tire reinforcement applications.

The same applies to the disclosure of the CN106929937 A. This relates to fibers made of polyamide 56.

According to invention, a reinforcement cord for elastomeric articles comprising two or more plies of polymeric materials, wherein at least one of the ply of the said reinforcement cord is comprised of polyamide 56 yarn (Figure 1).

According to the invention, the tenacity value of the said polyamide 5.6 yarn measured under ASTM conditions is minimum 7.5g/dtex in order to be comparable with polyamide 6.6. The tenacity less than 7.5g/dtex does not provide the required strength with acceptable rivet area between cords or acceptable gauge which is important for reduced rolling resistance due to increased rubber content in tire.

According to the invention the twist level of the reinforcement cord is minimum 100 and maximum 500 twist per meter (tpm). The twist level less than lOOtpm does not provide the required fatigue resistance under cyclic tension and compression. The twist level higher than 500 tpm gives rise to the too high strength reduction which is important for burst strength of the tire.

According to the invention the total linear density of the reinforcement cord is between 600 and 6,000 dtex. The reinforcement cord having a linear density less than 500dtex means too high cord density (ends per decimeter, epdm) or increased number of layer which are not preferred for the reduced heat generation (inter-cord and interply shear strains) in tire. The reinforcement cord having a linear density higher than 6,000dtex hast too high cord thickeness resulting in increased rubberized layer gauge and negative effect on cord fatigue resistance.

The unit "dtex" is known to the person skilled in the art and is a measure of the weight per length. The lower the fineness in dtex, the lighter the corresponding yarn or cord. According to the invention, a reinforcement cord is characterized in that it contains at least one further ply, wherein the at least one ply of the said reinforcement cord is comprised of polyamide 56 yarn and the at least one further ply selected a list comprising of polyamide 66, recycled polyamide 66, polyamide 56, polyamide 46, polyamide 4.10, biobased polyamide, polyamide 6, polyketone, polyethylene terephthalate (PET), recycled PET, biobased PET, rayon, aramid type materials or a combination thereof (Figure 2).

For the purposes of the present invention, "recycled PET" is PET which has been obtained from PET waste products by a chemical or a mechanical method.

For the purposes of the present invention, "recycled polyamide 66" is polyamide which has been obtained from polyamide 66 waste products by a chemical or a mechanical method.

For the purposes of the present invention, “biobased polyamide“ is a new class of bioplastics that are derived from renewable resources such as natural fats and oils. A biobased polyamide fiber according to the invention, wherein the polyamide is selected from the group consisting of: polyamide 4, polyamide 4.6, polyamide 4.10; polyamide 5.X, wherein X is an integer from 4 to 16; polyamide 6, polyamide 6.6, polyamide 6.9, polyamide 6.10; polyamide 6.12; polyamide 10.10; polyamide 10.12; polyamide 11; polyamide 12; polyamide 12.12; and mixtures thereof.

Within the scope of the present invention, cords are linear structures which consist of two or more yarns twisted together.

In order to fullfil some spesific reinforcement requirements sometimes it is necessary to combine different polymeric yarns having different tensile and thermal properties which are called as hybrid cords in the tire technology. The hybrid cords in the tire applications usually combine at least two different cord plies with different modulus or LASE values.

In usual prior art applications, the high modulus ply yarn is aramid and low modulus ply yarn is polyamide 6.6. having bielastic stress-strain behaviour.

According to invention polyamide 6.6 yarn in conventional hybrid cord can replaced with wholly or partially bio-based polyamide 6.6 yarn with similar cord tensile properties.

According to invention, a reinforcement fabric consisiting of parallel cords in which polyamide 6.6 and polyamide 5.6 cords are arranged sequentially (alternately) in said reinforcement fabric (Figure 3). The polyamide 5.6 cord in the fabric is at least partially bio-based and environmetally friendly. The alternately placed polyamide 6.6 and polyamide 5.6 cords dipped and heat-set under the same hot-stretching process parameters (Tension, Temperature and Time) have different modulus or extensibilities. The different cord extensibilities in carcass or capply creates a reinforcement plane with zig-zag cross-section having enhanced ply separation resistance under high speed conditions resulting improved tire durability and performance

According to invention, a reinforcement fabric comprising parallel paired cords wherein each individual paired cord in reinforcement fabric comprises one polyamide 5.6 cord and one polyamide 6.6 (Figure 4). The polyamide 5.6 cord in the fabric is at least partially bio-based and environmetally friendly. The paired cords having flat cross-section enables gauge and rubber reduction in reinforcement layer in tire.

According to invention, a reinforcement fabric comprising parallel paired cords wherein each individual cord in pair is hybrid cord consisting of at least one ply polyamide 5.6 yarn and at least one ply polyamide 6.6 yarn. (Figure 5) The polyamide 5.6 cord in the fabric is at least partially bio-based and environmentally friendly. The paired cords having flat cross-section enables gauge and rubber reduction in reinforcement layer in tire.

According to invention, the reinforcement cord is a hybrid cord comprising polyamide 6.6 and polyamide 5.6 plies.

According to invention, the reinforcement cord is a hybrid cord comprising Aramid and polyamide 5.6 plies.

According to invention, the reinforcement cord is a hybrid cord comprising polyethylene terephthalate and polyamide 5.6 plies.

According to invention, the reinforcement cord is a hybrid cord comprising recycled PET (polyethylene terephthalate) and polyamide 5.6 plies.

According to invention, nylon 6.6 and bio-based nylon 5.6 cords are arranged sequetially(alternately) as parallel cords in a tire cord fabric having hybrid behaviour under tensile forces.

The said cords according to the inventions are used as reinforcement in pneumatic tires.