Table tennis racket rubber

Abstract

The present invention relates to a table tennis racket rubber (B) having an integral elastomer body (E) made of a fully crosslinked elastomer matrix material. The elastomer body (E) has a foamed inner region (C) and a smooth outer surface (A). The rubber (B) is manufactured by a two-step vulcanization process according to the method of the present invention, in which a partially vulcanized blank (H) expands by adding a foaming agent between a first incomplete vulcanization step (8) and a second vulcanization step (12). In one method embodiment, the elastomer body (E) is formed by co-vulcanization with a combination of two blank layers (S1, S2) to which a foaming agent is added to at least one for the formation of a foamed inner region (C).

Description

[Technical Field]

[0001] This invention relates to table tennis racket rubber, and to a method for manufacturing the same. [Background technology]

[0002] Traditional table tennis racket rubber typically consists of two layers: a non-foamed upper layer with pips that forms the outer layer of the rubber (facing away from the racket's wood) when assembled, and a foamed lower layer that is positioned between the upper layer and the racket's wood when assembled. Both of these layers are usually manufactured from fully crosslinked elastomer (rubber). Therefore, the upper layer is also called "upper rubber" or "pip rubber," and the lower layer is also called "sponge."

[0003] The primary role of the upper rubber is often to ensure the best possible adhesion between the ball and the racket upon impact, thereby particularly ensuring the reversal or enhancement of ball spin during the shot. However, there are also "anti-spin rubbers" that aim to achieve relatively low adhesion. The primary role of the sponge is usually to efficiently transfer the kinetic energy of the shot to the ball, thereby accelerating the ball as powerfully as possible. The strength of the adhesion between the ball and the racket mediated by the rubber is also called the rubber's "grip." The rubber's ability to transfer kinetic energy to the ball and, consequently, accelerate the ball is also called the rubber's "speed."

[0004] The two layers of rubber are usually manufactured separately from each other. The sponge is cut as a thin layer from a block of rubber sponge (cellular rubber) and bonded to the upper rubber with an elastic adhesive. The rubber thus formed is then bonded to the racket wood with yet another adhesive layer during the assembly process, thereby placing the sponge between the racket wood and the upper rubber.

[0005] In most cases, the upper rubber is mounted on the racket with the pips facing inward, and consequently, the smooth surface of the upper rubber facing outward. However, as an alternative, there are rackets where the piped side of the upper rubber faces outward when assembled. Rackets with outward-facing pips often lack a sponge. In this case, the upper rubber is mounted directly onto the wood. Rubber consisting only of upper rubber can be manufactured in a particularly simple and convenient way, as the steps for manufacturing the sponge and bonding both layers are omitted. However, such rubber is often of low quality, and in particular, usually has very low grip and speed. [Overview of the project] [Problems that the invention aims to solve]

[0006] The objective of this invention is to simplify the manufacturing process of high-quality table tennis racket rubber. [Means for solving the problem]

[0007] With regard to (table tennis racket) rubber, this problem is solved by the constituent element of claim 1 according to the present invention. With regard to a method for manufacturing rubber, this problem is solved by the constituent element of claim 9 according to the present invention. Preferred embodiments of the present invention, which are inventive when viewed in part on their own, are described in the dependent claims and the following description.

[0008] Unlike conventional high-quality rubber, which consists of two rubber layers bonded together, the rubber according to the present invention is composed of a single, integrated rubber layer (i.e., a single, integrated elastomer body consisting of a fully crosslinked elastomer matrix material).

[0009] On the other hand, unlike rubbers that consist only of an upper rubber layer (i.e., a single, integrated rubber layer, as used in inexpensive rackets or rackets that do not reverse ball spin), the integrated elastomer body of the rubber according to the present invention performs both the function of the upper rubber and the function of a sponge. To this end, the elastomer body has a foamed inner region and a smooth (or non-porous) outer surface. Here, "foamed" means that the elastomer body has a foamy or sponge-like structure in its inner region, in which a matrix material surrounds numerous hollow spaces ("pores") filled with gas. "Smooth" or "non-porous" means that the pores in the foamed inner region are closed toward the outer surface—unlike the sponge of a typical table tennis racket rubber. In this case, the rubber preferably has an edge region in contact with the outer surface where the elastomer body is not foamed, i.e., it does not have a foamy or sponge-like structure, and consequently, it does not have a gas-filled hollow space—except for occasional manufacturing errors or holes drilled after the vulcanization process.

[0010] Due to the synergistic effect of its smooth outer surface and foamed inner region, the rubber according to the present invention possesses speed and grip similar to conventional rubbers made of equivalent materials and with equivalent strength, having an upper rubber and a separately manufactured sponge. On the other hand, based on the integrated structure of the elastomer body, the rubber according to the present invention is characterized by significantly simplified manufacturing possibilities compared to such conventional rubbers.

[0011] In an embodiment of the rubber according to the present invention that can be manufactured more simply and therefore particularly rationally, the matrix material of the elastomer has a uniform elastomer composition. In other words, the elastomer is formed by a single rubber layer made of a single rubber material, in which a foamed inner region and an edge region forming a smooth outer surface transition to each other without material boundaries of the matrix material.

[0012] In such a single-layer form of rubber, the elastomer body preferably has a thickness of 1.5 to 6 mm. The foamed inner region of the single-layer elastomer body has a density of 0.3 to 0.9 g / cm³ under preferred dimensional settings. 3 It has a density of [grams per cubic centimeter], while the matrix material of the elastomer itself (not considering the gas-filled pores contained within the inner region) has a density of 0.8-1.5 g / cm³. 3 It has a density of .

[0013] In a more complex, but more flexible and higher-quality, configuration of rubber, the elastomer comprises an upper and lower layer directly bonded to each other. The lower layer constitutes a foamed inner region, while the upper layer forms a smooth outer surface. Unlike conventional rubber, the upper and lower layers are manufactured using a common process. Specifically, the upper and lower layers are manufactured by co-vulcanization, during which they are simultaneously bonded to each other.

[0014] Here and below, “material bonding” or “material bonding formula” is understood to mean that each bonded part is integrated at its respective contact surface by the fusion or cross-linking of materials (for example, based on the bonding forces of atoms or molecules, i.e., by covalent bonding). The material bonding formula between the two layers of rubber is “direct” in the sense that there is no bonding medium interposed between the two layers, particularly an adhesive. That is, the adhesive layer that bonds the two layers, which are manufactured separately in conventional rubber, is absent in the rubber according to the present invention.

[0015] In this embodiment, it is preferable that the upper layer is not foamed throughout its entire thickness. Therefore, the entire upper layer constitutes a non-foamed edge region that also forms a smooth outer surface. In an alternative embodiment, the upper layer also has foaming in the region in contact with the lower layer.

[0016] The upper layer preferably has a thickness of 0.1 to 2 mm (particularly between 0.5 mm and 2 mm), and the lower layer preferably has a thickness of 1.5 to 6 mm (particularly between 2 mm and 5 mm). The density of the lower layer forming the foamed inner region of the rubber is 0.3 to 0.9 g / cm³ under preferred dimensional settings. 3 The upper layer contains 0.5 g / cm³. 3 From 1.5 g / cm³ 3 It is preferable to have a density between these values, and this density also depends on how strongly the foaming of the upper layer, which may be present, is manifested. The matrix material itself should be 0.8 to 1.5 g / cm³ in both layers of the multilayer rubber. 3 It is preferable that it has a density of [value].

[0017] In the method according to the present invention, the rubber is manufactured by a two-step vulcanization process, in which a foaming agent is added between the first incomplete vulcanization step and the second vulcanization step to expand the partially vulcanized blank. Here and below, "vulcanization" refers to the process that leads to the production of the vulcanized final product, i.e., a fully crosslinked elastomer. The designations "vulcanization~" (i.e., vulcanization step, vulcanization time, vulcanization temperature, etc.) represent individual steps or quantities in the vulcanization process, even if they do not lead to the vulcanized final product.

[0018] To produce a single layer of rubber according to the present invention, in a first embodiment of the method according to the present invention, in a first mixing step, an unreactive starting material of the elastomer composition is first mixed to form a premix, preferably using a closed mixer. The unreactive starting material of the elastomer composition comprises at least one polymer (i.e., a pure polymer or a polymer mixture), zinc oxide, and, optionally, at least one plasticizer and / or at least one filler. As the polymer, natural rubber or synthetic rubber, particularly EPDM, is used in various embodiments of the present invention.

[0019] In a second mixing step, reactive starting materials for the elastomer composition are added to the premixture—preferably using a rolling mill or a closed mixer. The reactive starting materials include at least one accelerator (preferably at least one primary accelerator and at least one secondary accelerator), sulfur, and a blowing agent. As a result of the second mixing step, a plastically deformable material called an elastomer blank is obtained.

[0020] Then, a two-stage vulcanization process is carried out from this blank to produce an (fully crosslinked) elastomer and the resulting finished rubber. In this process, the blank is first partially vulcanized in the first vulcanization step at a first vulcanization temperature for the duration of the first vulcanization time. Here, "partially vulcanized" (also called "pre-vulcanized") means that the first vulcanization step is completed before the vulcanization process for forming the elastomer material, i.e., the complete crosslinking of the polymer, is completed. Thus, the final product of the first vulcanization step is a partially vulcanized semi-finished product (also called a "partially vulcanized blank") in which the polymer material it contains is only partially vulcanized.

[0021] During and / or thereafter, the partially vulcanized semi-finished product expands (also called "bulging") under the action of a foaming agent that decomposes due to the effect of temperature, thereby stretching the partially vulcanized semi-finished product while forming pores (also called "cell formation"). Under this expansion process, the foamed inner region of the elastomer is formed.

[0022] In the second vulcanization step, the (partially vulcanized and) expanded semi-finished product (also referred to as the "expanded blank") is vulcanized under the second vulcanization temperature for the duration of the second vulcanization time. Here, the concept of "fully vulcanized" means that the second vulcanization step is carried out until the vulcanization reaction is completed, that is, until a fully cross-linked elastomer body is formed. For example, the first vulcanization step and the second vulcanization step are set such that the first vulcanization time is between 5% and 25% of the second vulcanization time, particularly approximately 10%. Accordingly, the first vulcanization time is between approximately 4.5% and 20% of the total vulcanization time - resulting from the sum of the first and second vulcanization times - particularly approximately 9%.

[0023] The second aspect of the method according to the invention serves to manufacture a multi-layer (particularly two-layer) rubber aspect according to the invention. This method aspect is the same as the method described above, except for the differences described in detail below. However, in the first mixing step, for forming both blank layers, the non-reactive starting materials of the first elastomer composition and the non-reactive starting materials of the second elastomer composition are mixed to form the first preliminary mixture or the second preliminary mixture. At this time, the non-reactive starting materials of the first and second elastomer compositions each contain at least one polymer (i.e., a pure polymer or a polymer mixture), zinc oxide, and - optionally - at least one plasticizer and / or at least one filler material.

[0024] In the second mixing step, both preliminary mixtures are further processed to form the first to second blank layers by adding the reactive starting materials of the first to second elastomer compositions. At this time, the reactive starting materials of the first and second elastomer compositions each contain at least one accelerator and sulfur. The reactive starting material of the second elastomer composition additionally contains a blowing agent.

[0025] In the subsequent combination step, both blank layers are placed planarly on top of each other and joined together to form a single blank, particularly by the application of a crimping force by a crimping roll or crimping roller.

[0026] Then, this blank, formed by combining both blank layers, is manufactured in accordance with the manufacturing process of the single-layer rubber described above. - In the first vulcanization step, the material is first partially vulcanized at a first vulcanization temperature for the duration of the first vulcanization time. - During and / or thereafter the first vulcanization step, the elastomer expands as a result of pressure generation by the decomposition of the foaming agent, in order to form a foamed inner region of the elastomer, - Under a partially vulcanized and expanded state, the material is fully vulcanized at a second vulcanization temperature for the duration of a second vulcanization time to form a fully crosslinked elastomer.

[0027] The first and second vulcanization steps are carried out in different molds (i.e., a first mold and a second mold) in both embodiments of the method, and in a convenient embodiment of the method, the two molds are distinguished by the depth of the cavity they enclose when closed. The second mold leaves more space for the (already expanded) semi-finished product than the first mold. The first mold is preferably configured to be airtight when closed in order to prevent the gaseous foaming agent from escaping during the first vulcanization step. Optionally, the second mold may also be configured to be airtight when closed.

[0028] The method according to the present invention (in both method embodiments described above) corresponds in terms of its fundamental character to an expansion method applied for the manufacture of cellular rubber, such as the one described in German Patent No. 821 423 B. Details of the implementation of the method according to the present invention are supplemented by the above-mentioned literature.

[0029] The starting materials for the elastomer composition of a single layer of rubber, or the elastomer composition of both layers of rubber, preferably include, in addition to -100 phr of each polymer or polymer mixture, the following: - Zinc oxide at 2-10 phr, - 0-2 phr of stearic acid, - Filling material with 0-40 phr, especially magnesium carbonate or chalk, - Plasticizers with a concentration of 0-30 phr (especially 10-30 phr), particularly naphthenic oils or phthalates. - 1-3 phr sulfenamide-based primary accelerators, especially TBBS or CBS, - 0-2.5 phr thiram-based, dithiocarbamate-based, and / or dithiophosphate-based secondary accelerators, particularly TMTD, TMTM, ZBEC, ZDMC, or TP. - Vulcanization retarders of 0-2 phr, especially N-phenyl-N-[(trichloromethyl)thio]benzenesulfonamide), and - Sulfur at 0.5-4 phr.

[0030] Starting materials with a lower quantity limit of 0 phr are optional components.

[0031] In a method embodiment for producing a single layer of rubber, the starting material of the (single) elastomer composition additionally contains 1 to 5 phr of a foaming agent, particularly OBSH. In a method embodiment for producing a two-layer rubber, the starting material of the second elastomer composition (preferably only the starting material) additionally contains 1 to 5 phr of a foaming agent, particularly OBSH.

[0032] The polymers or polymer mixtures used within the framework of this invention include natural rubber or synthetic rubber, particularly ethylene-propylene-diene-rubber (EPDM).

[0033] The designation "phr" (parts per hundred rubber) is a widely used unit of measurement in rubber manufacturing, where the total amount of rubber in the starting materials of an elastomer composition is calculated to equal 100%. All other components of the starting materials, especially fillers, plasticizers, accelerators, and vulcanization retarders, are added, and as a result, the total amount of starting materials expressed in phr usually exceeds 100%.

[0034] In the method embodiment for producing two layers of rubber, it is also preferable that the starting materials for both elastomer compositions differ, regardless of the proportion of the foaming agent. However, in some embodiments of the present invention, both elastomer compositions are partially identical, in particular with respect to the polymers used, and, optionally, with respect to other components of each composition, such as the same proportion of zinc oxide, the same filler, the same proportion of zinc oxide, stearic acid, or sulfur, and / or the same accelerator. In such cases, one or more steps for producing the first blank layer and the second blank layer are preferably—as far as possible—performed jointly. For example, in certain embodiments of the present invention, the first and second elastomer compositions may rely on unreactive starting materials of the same composition. In such cases, it is preferable that the first mixing step, and, optionally, part of the second mixing step, be performed jointly for both elastomer compositions. In particular, both premixtures are separated only before the selective addition of the foaming agent.

[0035] In summary, the subject of the present invention is a table tennis racket rubber having an integral elastomer body made of a fully vulcanized elastomer matrix material. The elastomer body has a foamed inner region and a smooth outer surface. This rubber is manufactured by a two-step vulcanization process according to the method of the present invention, in which a partially vulcanized blank to which a foaming agent has been added expands between a first incomplete vulcanization step and a second vulcanization step. In one embodiment of the method, the elastomer body is formed by co-vulcanization with a combination of two blank layers to which a foaming agent has been added to at least one for the formation of a foamed inner region. Compared with conventional rubbers that consist of two layers bonded together, i.e., a granular layer and a sponge layer, in the manufacture of the rubber according to the present invention, one of the two vulcanization processes and the bonding process are omitted. Therefore, the rubber according to the present invention can be manufactured much more simply and at a lower cost while maintaining equivalent quality.

[0036] Similarly, unlike conventional rubbers formed from a granular layer and a sponge layer bonded thereto, in the multilayered form of rubber according to the present invention, the upper layer does not have granules, and in particular, the side facing the lower layer does not have granules.

[0037] The method according to the present invention is particularly aimed at the production of table tennis racket rubber made of an elastomer body that is always manufactured integrally, whether in single or multilayer form. Therefore, a special embodiment of this method is that the elastomer body obtained as a result of the method according to the present invention is used as table tennis racket rubber.

[0038] Next, embodiments of the present invention will be described in detail with reference to the drawings. [Brief explanation of the drawing]

[0039] [Figure 1]This is a schematic flowchart illustrating a method for manufacturing (table tennis racket) rubber, which is formed from a single elastomer body consisting of a fully crosslinked elastomer matrix material. The elastomer body consists of a foamed lower layer and a non-foamed upper layer with a smooth outer surface. The lower and upper layers are jointly manufactured by co-vulcanization and directly bonded to each other in a material bonding formula. [Figure 2] This is a cross-sectional photograph showing an example of rubber manufactured according to the method in Figure 1. [Figure 3] Figure 1 is a similar drawing to illustrate an alternative method for manufacturing (table tennis racket) rubber, in which an integral elastomer body is formed from a fully crosslinked elastomer matrix material having a uniform elastomer composition, and the elastomer body similarly has a foamed inner region and a smooth outer surface. [Figure 4] This is a drawing similar to Figure 2, showing an example of rubber manufactured according to the method in Figure 3. [Modes for carrying out the invention]

[0040] Corresponding parts and structures are always given the same reference numerals in all drawings.

[0041] 1. A method for producing rubber B from two layers of elastomer E: Figure 1 illustrates a method for manufacturing (table tennis racket) rubber B, shown exemplifyingly in Figure 2, which is formed from two layers of fully crosslinked elastomer matrix material (i.e., rubber). Both layers, i.e., the upper layer O and the lower layer U, are jointly manufactured by co-vulcanization, thereby directly bonded together in a material bonding manner. In this case, the upper layer O and the lower layer U are not separated by any adhesive layer; that is, they are an integrally manufactured elastomer body E. The upper layer O faces outward when rubber B is assembled onto the wood of the (table tennis) racket. In the illustrated example, this upper layer O is not foamed and has a smooth, i.e., non-porous outer surface A. The lower layer U is positioned between the upper layer O and the wood of the racket when rubber B is assembled. The lower layer has a foamy or spongy structure, that is, it has numerous hollow spaces (also called pores P) filled with gas, thus forming the foamed inner region C of the rubber B.

[0042] The method begins with a first mixing step 2, in which the unreactive starting materials of a first elastomer composition are mixed separately in a closed mixer to form a first premixture V1 (partial step 2a), and the unreactive starting materials of a second elastomer composition are mixed to form a second premixture V2 (partial step 2b). The unreactive starting materials of the first and second elastomer compositions each comprise a polymer and zinc oxide, and, optionally, a plasticizer and / or one or more fillers. - 100 phr polymers, especially natural rubber or synthetic rubber (especially EPDM), - Zinc oxide at 2-10 phr, - 0-2 phr of stearic acid, - Filling material with a value of 0-40 phr, such as magnesium carbonate or chalk, and - Plasticizers with a value of 0-30 phr, such as naphthenic oils or phthalates.

[0043] Next, in the second mixing step 4, the rolling mill adds the reactive starting materials for the first elastomer composition to the first premixture V1 (partial step 4a). Separately, the rolling mill also adds the reactive starting materials for the second elastomer composition to the second premixture V2 (partial step 4b). The reactive starting materials for both elastomer compositions include sulfur, a primary accelerator, and a secondary accelerator, respectively. For example, - 1-3 phr of sulfenamide-based primary accelerator, e.g., TBBS or CBS, - 0-2.5 phr thiram-based, dithiocarbamate-based, and / or dithiophosphate-based secondary accelerators, e.g., thiram: TMTD, TMTM; dithiocarbamate: ZBEC, ZDMC; dithiophosphate: TP - A vulcanization retarder of 0-2 phr, such as Vulkalent E (chemical name: N-phenyl-N-[(trichloromethyl)thio]benzenesulfonamide)), and - Sulfur at 0.5-4 phr.

[0044] To the second preliminary mixture V2, a blowing agent (e.g., OBSH) is added and mixed in an amount ratio of, for example, 1 to 5 phr, as an additional starting material for the second elastomer composition.

[0045] The respective reactive starting materials are further mixed to process the first premixture V1 into a first blank layer S1 and the second premixture V2 into a second blank layer S2. The first blank layer S1 has a thickness of, for example, 0.1 to 2.0 mm (particularly 0.5 to 2.0 mm). The second blank layer S2 has a thickness of, for example, 1.0 to 2.5 mm.

[0046] In the subsequent combination step 6, both blank layers S1 and S2 are placed planarly on top of each other. The blank layers S1 and S2, placed on top of each other, are pressed together by a crimping roll or crimping roller, thereby directly joining them to form a blank R. After combination step 6, the blank R has a thickness of, for example, 1.1 to 3.5 mm.

[0047] Subsequently, the elastomer body E is manufactured from this blank R through a two-stage vulcanization process.

[0048] To this end, in the first vulcanization step 8, the blank R is inserted into the cavity of a first heatable mold made of metal, where it is exposed to a first vulcanization temperature for the duration of the first vulcanization time. For example, the cavity of the first mold has a planar rectangular contour with a depth of, for example, 1.0 to 3.4 mm. The blank R is cut to completely fill the cavity of the first mold. At this time, the first vulcanization time and the first vulcanization temperature are selected so that the blank R is only partially vulcanized and the vulcanization process is not completed. For example, the first vulcanization time is only about 5% to 20% of the total vulcanization time that would be necessary for the completion of the vulcanization reaction, i.e., for the complete crosslinking of the elastomer material. Furthermore, the heat supply in the first vulcanization step 8 causes the foaming agent to decompose with gas generation. The first mold is designed to hermetically seal the cavity it surrounds, thereby preventing the gas released from the foaming agent from escaping.

[0049] After the first vulcanization time has elapsed, the first mold is opened in the expansion step 10. At this time, the partially vulcanized semi-finished product H formed from the blank R by the first vulcanization step 8 expands (swells) due to the action of gas released from the foaming agent, thereby forming the foamed inner region C of the rubber B. Throughout the first vulcanization time, the degree of crosslinking after the first vulcanization step 8, and consequently the degree of expansion, is controlled.

[0050] And in order to carry out the second vulcanization step 12, a partially vulcanized and expanded semi-finished product H' is inserted into a second heatable mold made of metal, having a deep cavity compared to the first mold, for example having a depth between 2 and 6 mm. In the second mold, the expanded semi-finished product H' is exposed to a second vulcanization temperature for the duration of the second vulcanization time. The second vulcanization time and the second vulcanization temperature are set such that the expanded semi-finished product H' is fully vulcanized in the second vulcanization step 12, i.e., such that the vulcanization reaction is completely concluded. As a result of the second vulcanization step 12, a fully cross-linked elastomer body E is produced. After the second mold is opened, the elastomer body E has a thickness of for example 2 to 6 mm, and the non-foamed upper layer O has a thickness of 0.1 to 2.0 mm, particularly approximately 0.5 mm.

[0051] In the final finishing step 14, the thus completed rubber B is cut or punched to the final dimensions, for example 17×17 cm. Further optionally, the elastomer body E is cut or chamfered at the inner surface I (Figure 2) facing the outer surface A, so that - as in the case of the sponge of a normal table tennis racket rubber - the porous structure of the lower layer U appears outside at the inner surface I.

[0052] In the completed rubber B, the matrix material of the elastomer body E has a density between 0.8 g / cm 3 and 1.5 g / cm 3 both in the upper layer O and in the lower layer U (without considering the gas-filled pores). Considering the pores, the density of the lower layer U is between 0.3 g / cm 3 and 0.9 g / cm 3 . The completed rubber B has a thickness particularly between 2 mm and 6 mm.

[0053] 1.1 Example 1 (two-layer rubber B based on natural rubber): In the first example of a two-layer rubber B that can be produced based on the method shown in Figure 1, the following were used respectively as starting materials for the elastomer compositions of the upper layer O and the lower layer: - In partial step 2a of the first mixing step 2, to produce the first premixture V1 (for forming the upper layer O): - 100 phr natural rubber, - 5 phr zinc oxide, - 2 phr black pigment - 20 phr magnesium carbonate, - 1 phr of stearic acid, and, - 20 phr of naphthenic plasticizer, - In step 2b of the first mixing step 2, to produce the second premixture V2 (for forming the lower layer U): - 100 phr natural rubber, - 5 phr zinc oxide, - Titanium dioxide with 2.4 phr, - 20 phr magnesium carbonate, - 1 phr of stearic acid, and, - A naphthenic plasticizer with a concentration of 20 phr.

[0054] The first mixing step 2 was performed using a closed-type mixer for both the first premixture V1 and the second premixture V2.

[0055] For the production of the first blank layer S1, in a partial step 4a of the second mixing step 4, the following reactive starting materials were added and mixed to the first premixture V1: - CBS 3phr, - 2.6 phr of sulfur, - TMTD of 1 phr, and, - 1,2phr ZBEC.

[0056] For the production of the second blank layer S2, in a partial step 4b of the second mixing step 4, the following reactive starting materials were added and mixed to the second preliminary mixture V2: - 1.2 phr TBBS, - 3 phr of sulfur, - TMTD of 0.15 phr, and, - OBSH version 4.8phr.

[0057] The second mixing step 4 was performed by a rolling mill on both the first blank layer S1 and the second blank layer S2.

[0058] In combination step 6, the second blank layer S2 was rolled to a thickness of 1.9 mm. The first blank layer S1 was rolled to a thickness of 0.3 mm and mounted planarly onto the second blank layer S2 using a pressure roll to form the blank R.

[0059] The first vulcanization step 8 was performed in the first mold for a first vulcanization time of 150 s at a first vulcanization temperature of 140°C.

[0060] The second vulcanization step 12 was carried out in the second mold for a second vulcanization time of 1500 s at a second vulcanization temperature of 140°C.

[0061] Figure 2 shows a cross-sectional photograph of the elastomer body E of rubber B obtained as a result of Example 1. This cross-sectional photograph shows an upper layer O with a smooth, unfoamed outer surface A and a lower layer U that is foamed (i.e., has numerous pores P).

[0062] 1.2 Example 2 (Two-layer rubber B based on EPDM for the upper layer O and natural rubber for the lower layer U): In a second example of a two-layer rubber B that can be manufactured according to the method shown in Figure 1, the following were used as starting materials for the elastomer composition of the upper layer O and the lower layer U, respectively: - In partial step 2a of the first mixing step 2, to produce the first premixture V1 (for forming the upper layer O): - 100 phr EPDM rubber (moderate ethylene and ENB content; model used: Keltan ECO 8550), - 5 phr zinc oxide, - 2 phr black pigment - 20 phr magnesium carbonate, - 1 phr of stearic acid, and, - A naphthenic plasticizer with a concentration of 20 phr.

[0063] - In step 2b of the first mixing step 2, to produce the second premixture V2 (for forming the lower layer U): - 100 phr EPDM rubber (moderate ethylene and ENB content; model used: Keltan ECO 8550), - 5 phr zinc oxide, - Titanium dioxide with 2.4 phr, - 20 phr magnesium carbonate, - 1 phr of stearic acid, and, - A naphthenic plasticizer with a concentration of 20 phr.

[0064] For the production of the first blank layer S1, in a partial step 4a of the second mixing step 4, the following reactive starting materials were added and mixed to the first premixture V1: - CBS 2phr, - 1.8 phr of sulfur, - TMTD of 1 phr, and, - 1.5 phr ZBEC.

[0065] For the production of the second blank layer S2, in a partial step 4b of the second mixing step 4, the following reactive starting materials were added and mixed to the second preliminary mixture V2: - 1.2 phr TBBS, - 0.9 phr of sulfur, - TMTD of 0.4 phr, - 1phr Vulkalent E, and, - OBSH version 4.8phr.

[0066] Combination step 6, first vulcanization step 8, expansion step 10, and second vulcanization step 12 were carried out in accordance with Example 1. However, unlike Example 1, the first vulcanization step 8 and the second vulcanization step 12 were carried out at a (first or second) vulcanization temperature of 170°C. The duration of the first vulcanization was 180 s. The duration of the second vulcanization was -1500 s, the same as in Example 1.

[0067] 2. Method and embodiment for producing rubber B consisting of a single layer of elastomer body E: Figure 3 shows a simplified embodiment of the method by which the elastomer body of rubber B is manufactured in a single layer with a uniform elastomer composition.

[0068] The method shown in Figure 3 is similar to the method in Figure 1 in terms of its basic procedure, and therefore the above explanation is applied. However, in the first mixing step 2, instead of (both premixtures V1 and V2), only a single premixture V is produced from the unreactive starting material of the elastomer composition.

[0069] In the second mixing step 4, the reactive starting materials for the elastomer composition, including the blowing agent, are added and mixed to this preliminary mixture V. In the method embodiment shown in Figure 3, the resulting blank R is obtained directly from the second mixing step 4. The combination step 6 of the method shown in Figure 1 is omitted here.

[0070] With respect to the first vulcanization step 8, the expansion step 10, the second vulcanization step 12, and the optional final finishing step 14, the method shown in Figure 3 is similar to the method shown in Figure 1.

[0071] In the completed rubber B, the matrix material of elastomer E (excluding gas-filled pores) is 0.8 g / cm³. 3 From 1.5 g / cm³ 3 It has a density between [value]. Considering pores, the density of elastomer E is 0.3 g / cm³. 3 From 0.9 g / cm³ 3 It is between these two ranges. The finished rubber, in particular, has a thickness between 2mm and 6mm.

[0072] 2.1 Example 3 (Single-layer rubber B based on natural rubber): In a first example of a single-layer rubber B that can be manufactured according to the method shown in Figure 3, the following were used as starting materials for the production of the premixture V in the first mixing step 2: - 100 phr natural rubber, - 5 phr zinc oxide, - 2.4 phr titanium dioxide - 20 phr magnesium carbonate, - 1 phr of stearic acid, and, - A naphthenic plasticizer with a concentration of 20 phr.

[0073] Pre-mixture V is also produced in a closed-type mixer.

[0074] For the production of blank R, in the second mixing step 4, the following reactive starting materials were added to the preliminary mixture V and mixed: - TBBS:1.2phr - Sulfur: 3phr - TMTD:0.15phr - OBSH:4.8phr The first vulcanization step 8 was performed in the first mold at a first vulcanization temperature of 140°C for a first vulcanization duration of 150 s.

[0075] The second vulcanization step 12 was carried out in the second mold at a second vulcanization temperature of 140°C for a second vulcanization duration of 1500 s.

[0076] Figure 4 shows a cross-sectional photograph of the elastomer body E of rubber B obtained as a result of Example 3. In this cross-section, the foamed inner region C and the smooth (i.e., poreless) outer surface A of the elastomer body E can be seen. Furthermore, compared to the two-layer rubber shown in Figure 2, it is clear that in Figure 4, there is a lack of layer boundaries inside the elastomer body E.

[0077] 2.2 Example 4 (Single-layer rubber B based on EPDM): In a second example of a single-layer rubber B that can be manufactured according to the method shown in Figure 3, the following were used as starting materials for the production of the premixture V in the first mixing step 2: - 100 phr EPDM rubber (moderate ethylene and ENB content; model used: Keltan ECO 8550), - 5 phr zinc oxide, - 2.4 phr titanium dioxide - 20 phr magnesium carbonate, - 1 phr of stearic acid, and, - A naphthenic plasticizer with a concentration of 20 phr.

[0078] For the production of blank R, in the second mixing step 4, the following reactive starting materials were added to the preliminary mixture V and mixed: - 1.2 phr TBBS, - 0.9 phr of sulfur, - TMTD of 0.4 phr, - 1phr Vulkalent E, and, - OBSH version 4.8phr.

[0079] In other respects, the preparation of the preliminary mixture V and the blank R was carried out in accordance with Example 3.

[0080] The first vulcanization step 8, the expansion step 10, and the second vulcanization step 12 were carried out in accordance with Example 3. However, unlike Example 3, the first vulcanization step 8 and the second vulcanization step 12 were carried out at a vulcanization temperature of 170°C (first or second). The duration of the first vulcanization was 180 s. The duration of the second vulcanization was -1500 s, the same as in Example 3.

[0081] The present invention will become particularly apparent with reference to the embodiments described above, but will not be limited to these examples. Rather, further embodiments of the present invention can be derived from the claims and the above description by those skilled in the art.

[0082] In the above description and claims, the following abbreviations and trademark names are used as synonyms for the following chemical substances (without being limited to specific commercial products): - CBS:N-cyclohexyl-2-benzothiadyl sulfenamide - ENB: Ethylene nor bornene - EPDM: Ethylene-propylene-diene-rubber - OBSH:p,p'-Oxybisbenzolsulfonylhydrazide - TBBS:N-tert.-butyl-2-benzothiadyl-sulfenamide - TMTD: Tetramethylthiuram disulfide - TMTM: Tetramethylthiuram monosulfide - TP: dithiophosphate - ZBEC: Zinc dibenzyl dithiocarbamate - ZDMC: Zinc-dimethyl-dithiocarbamate, - Vulkalent E:N-phenyl-N-[(trichloromethyl)thio]benzenesulfonamide [Explanation of symbols]

[0083] 2. (First) Mixing Step 2a, 2b Partial Steps 4. (Second) Mixed Step 4a, 4b Partial Steps 6 Combination Steps 8. (First) vulcanization step 10 Inflation Steps 12 (Second) vulcanization step 14 Finishing Steps A Exterior B (Table Tennis Racket) Rubber C (Foamed) Inner Region E Elastomer body H (partially vulcanized) semi-finished product H' (expanded) semi-finished product I. Inner self O upper layer P stoma R Blank S1 (First) Blank Layer S2 (Second) Blank Layer U lower layer V Premixture VI (First) Pre-mixture V2 (Second) Premixture

Claims

1. A table tennis racket rubber (B) having an integral elastomer body (E) made of a fully crosslinked elastomer matrix material, wherein the elastomer body (E) has a foamed inner region (C) and a smooth outer surface (A).

2. The table tennis racket rubber (B) according to claim 1, wherein the matrix material has a uniform elastomer composition.

3. The table tennis racket rubber (B) according to claim 2, wherein the foamed inner region (C) of the elastomer body (E) has a thickness of 1.5 to 6 mm.

4. The foamed inner region (C) of the elastomer body (E) is 0.3 g / cm³ ３ From 0.9 g / cm ３ The density is between 0.8 g / cm³, and the matrix material of the elastomer (E) is 0.8 g / cm³. ３ From 1.5 g / cm ３ Table tennis racket rubber (B) according to claim 2 or 3, having a density between the above.

5. The table tennis racket rubber (B) according to claim 1, wherein the elastomer body (E) comprises an upper layer (O) and a lower layer (U) that are directly bonded to each other in a material bonding manner, particularly by co-vulcanization, the lower layer (U) forms the foamed inner region (C), and the upper layer (O) has the smooth outer surface (A) formed on it.

6. The table tennis racket rubber (B) according to claim 5, wherein the upper layer (O) is not foamed over its entire thickness.

7. The table tennis racket rubber (B) according to claim 5 or 6, wherein the upper layer (O) has a thickness between 0.1 mm and 2 mm, and the lower layer (U) has a thickness between 1.5 mm and 6 mm.

8. The upper layer (O) has a density between 0.5 g / cm ３ and 1.5 g / cm ３ , the lower layer (U) has a density between 0.3 g / cm ３ and 0.9 g / cm ３ , and the matrix materials of the upper layer (O) and the lower layer (U) each have a density between 0.9 g / cm ３ and 1.5 g / cm ３ The table tennis racket rubber (B) according to any one of claims 5 to 7.

9. A method for manufacturing a table tennis racket rubber (B) according to any one of claims 1 to 8, wherein the elastomer body (E) is manufactured by a two-step vulcanization process, wherein a foaming agent is added between a first incomplete vulcanization step (8) and a second vulcanization step (12) to expand a partially vulcanized blank (R).

10. - An elastomer composition of non-reactive starting material is mixed to form a premixture (V), wherein the elastomer composition of non-reactive starting material comprises at least one polymer or polymer mixture and zinc oxide. - For the formation of the elastomer body (E) and the blank (R), a reactive starting material of the elastomer composition is added and mixed into the premixture (V), wherein the reactive starting material of the elastomer composition comprises at least one accelerator, sulfur, and a blowing agent. - The blank (R) is partially vulcanized in the first vulcanization step (8) at a first vulcanization temperature for the duration of the first vulcanization time, - For the formation of the foamed inner region (C) of the elastomer body (E), the partially vulcanized blank (H) expands under the expansion of the foaming agent, and, - For the formation of a fully crosslinked elastomer body (E), the expanded blank (H') is fully vulcanized in a second vulcanization step (12) at a second vulcanization temperature for the duration of a second vulcanization time. The method according to claim 9 for manufacturing a table tennis racket rubber (B) according to any one of claims 1 to 4.

11. - The non-reactive starting materials of the first elastomer composition are mixed to form a first premixture (V1), and the non-reactive starting materials of the second elastomer composition are mixed to form a second premixture (V2), wherein the non-reactive starting materials of the first and second elastomer compositions each comprise at least one polymer or polymer mixture and zinc oxide. - In the above method, - To form the first blank layer (S1), the first premixture (V1) is further mixed with the reactive starting material of the first elastomer composition. - To form a second blank layer (S2), the reactive starting material of the second elastomer composition is added and mixed to the second premixture (V2). The reactive starting materials of the first elastomer composition and the second elastomer composition each contain at least one accelerator and sulfur, and the reactive starting materials of the second elastomer composition further contain a blowing agent. - Both blank layers (S1, S2) are placed planarly on each other and bonded together to form a blank (R) by applying a compressive force. - The blank (R) is partially vulcanized in the first vulcanization step (8) at a first vulcanization temperature for the duration of the first vulcanization time, - For the formation of the foamed inner region (C) of the elastomer body (E), the partially vulcanized blank (H) expands as a result of pressure generation due to the decomposition of the foaming agent, and, - For the formation of a fully crosslinked elastomer, the expanded blank (H') is fully vulcanized in a second vulcanization step (12) at a second vulcanization temperature for the duration of a second vulcanization time. The method according to claim 9 for manufacturing a table tennis racket rubber (B) according to any one of claims 5 to 8.

12. The starting materials for the aforementioned elastomer composition, or each of the elastomer compositions, are added to 100 phr of polymer or polymer mixture, particularly natural rubber or synthetic rubber, respectively: - 2 to 10 phr of zinc oxide - 0-2 phr stearic acid - Filling material with a density of 0 to 40 phr, especially magnesium carbonate or chalk. - Plasticizers in the range of 0 to 30 phr, especially naphthenic oils or phthalates, - 1-3 phr sulfenamide-based primary accelerators, especially TBBS or CBS, - 0-2.5 phr of thiram-based, dithiocarbamate-based, and / or dithiophosphate-based secondary accelerators, particularly TMTD, TMTM, ZBEC, ZDMC, or TP. - 0-2 phr vulcanization retarders, particularly N-phenyl-N-[(trichloromethyl)thio]benzenesulfonamide), and, - 0.5 to 4 phr of sulfur The method according to claim 10 or 11, including the method described in claim 10 or 11.

13. The method according to claims 10 and 12, wherein the starting material of the elastomer composition additionally comprises 1 to 5 phr of a blowing agent, particularly OBSH.

14. The method according to claims 11 and 12, wherein the starting material of the second elastomer composition additionally comprises 1 to 5 phr of a blowing agent, particularly OBSH.

15. The method according to any one of claims 10 to 14, wherein the first vulcanization time is between 5% and 25% of the second vulcanization time, and in particular about 10%.

16. Use of an elastomer (E) manufactured according to any one of claims 9 to 15, for use as table tennis racket rubber (B).

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