JP2011057374A - Rubber composition for conveyor belt and conveyor belt - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for a conveyor belt, which is satisfactory in an adhesive property with a brass plating steel cord, and has an excellent vulcanization speed, and to provide the conveyor belt satisfactory in durability and productivity of using the rubber composition. <P>SOLUTION: This conveyor belt is characterized by including zinc dimethacrylate by 1-2 pts.mass and cobalt neodecanoate boride by 2-3.5 pts.mass to 100 pts.mass of a rubber component, and is formed by arranging these between cover rubber layers 1 with the brass plating steel cord 3 covered with an adhesive rubber layer 2 composed of the rubber composition for the belt conveyor as a core body. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a rubber composition for a conveyor belt that is excellent in adhesiveness with a brass-plated steel cord, has a good vulcanization speed, and is excellent in mass production, and a conveyor belt using the rubber composition.

  Steel cords are widely used as a reinforcing material for rubber products such as conveyor belts. At that time, the adhesion between the rubber composition and the steel cord greatly affects the durability of the products.

  Conventionally, as a measure for satisfactorily bonding a steel cord and rubber, a method of combining rosin, an organic acid cobalt salt and an organic chlorine compound into a rubber (Patent Document 1: Japanese Patent Laid-Open No. 2006-31744), triazine , Zinc dimethacrylate, zinc diacrylate and organic acid cobalt in combination with rubber (Patent Document 2: JP-A-2005-350491), acid-modified polymer and zinc dimethacrylate in combination A method of blending with a rubber component (Patent Document 3: Japanese Patent Laid-Open No. 2006-176580) has been proposed.

  However, these conventional techniques can improve the adhesion between rubber and steel cord, but the use of organic acid cobalt or zinc dimethacrylate reduces the vulcanization rate, resulting in mass productivity and productivity. Incurs a decline.

  In addition, there is a lip guard type belt that uses a brass-plated steel cord as a breaker as a steel cord. With this type of belt, direct vulcanization bonding is performed using a brass-plated steel cord and adhesive rubber. In the case of the vulcanization production method using, there is inevitably a place where vulcanization occurs twice, and there is a possibility that adhesion will be reduced due to heat at that place. Further, since vulcanization is also performed in an endless process in which both ends are joined at the site of use and the belt is processed into a circumferential shape, the adhesion with the brass-plated steel cord is likely to occur again here.

  Therefore, it adheres well to brass-plated steel cords, has sufficient durability even when used in harsh environments such as humid environments and high temperature environments, and requires multiple heat treatments, and has a good vulcanization rate Development of a rubber composition for conveyor belts having high productivity and productivity is desired.

JP 2006-31744 A JP 2005-350491 A JP 2006-176580 A

  The present invention has been made in view of the above circumstances, and has a rubber composition for a conveyor belt that has excellent adhesion to a brass-plated steel cord and has a good vulcanization speed, and durability and productivity using the rubber composition. It aims at providing the conveyor belt which is excellent in.

  As a result of intensive studies to solve the above-mentioned problems, the present inventor, when adding and compounding zinc dimethacrylate and cobalt organic acid to rubber, in order to improve the adhesion to the brass-plated steel cord, Cobalt neodecanoate borate is used as the cobalt oxide, and by adjusting the blending ratio thereof, the adhesion with the brass-plated steel cord can be improved, and the rubber vulcanization rate is effectively improved. Even when a conveyor belt with excellent durability can be obtained with good productivity and a lip guard type conveyor belt using a brass-plated steel cord as a breaker is manufactured, multiple heating vulcanizations are required. The present invention has been completed by finding that good adhesiveness can be reliably obtained.

Therefore, the present invention
(1) A rubber composition for a conveyor belt, comprising 1 to 2 parts by mass of zinc dimethacrylate and 2 to 3.5 parts by mass of cobalt borate neodecanoate with respect to 100 parts by mass of the rubber component, as well as,
(8) In a conveyor belt in which a brass-plated steel cord covered with an adhesive rubber layer is disposed as a core between cover rubber layers, the adhesive rubber layer is formed of the rubber composition of the present invention. Conveyor belt features, and
(9) The conveyor belt according to (8), which is a lip guard type belt using a brass plated steel cord as a breaker.

  Further, as a result of further investigations, the present inventor has found that, as the rubber component, natural rubber or a mixed rubber obtained by mixing a synthetic rubber such as styrene-butadiene rubber (SBR) at a predetermined ratio is preferable, and a phenol resin. In particular, the inventors have found that the adhesiveness can be further improved by adding a predetermined amount of a phenol resin internally added with hexamethylenetetramine, β-naphthol, hexamethoxymethylated melamine (curing agent), or the like.

Therefore, this invention provides the rubber composition for conveyor belts of the following (2)-(7), and a conveyor belt as a suitable embodiment.
(2) The rubber composition for conveyor belts according to (1) above and (8) or (9) above containing 20-50 parts by weight of natural rubber and 80-50 parts by weight of synthetic rubber in 100 parts by weight of the rubber component. Conveyor belt.
(3) The conveyor rubber according to (1) or (2), wherein the synthetic rubber is one or more selected from styrene-butadiene rubber (SBR), butadiene rubber (BR), and isoprene rubber (IR). A rubber composition and the conveyor belt of (8) or (9) above.
(4) The rubber composition for a conveyor belt according to any one of (1) to (3) and 1 to 10 parts by mass of a phenol resin with respect to 100 parts by mass of a rubber component and the conveyor according to (8) or (9) above. belt.
(5) The rubber composition for a conveyor belt according to (4) and the conveyor belt according to (8) or (9), wherein the phenol resin is a resin in which hexamethylenetetramine is internally added.
(6) The rubber composition for conveyor belts according to any one of (1) to (5) above and (8) or (9) above containing 1 to 10 parts by mass of β-naphthol with respect to 100 parts by mass of the rubber component. Conveyor belt.
(7) For the conveyor belt according to any one of the above (1) to (6), containing 1 to 10 parts by mass of hexamethoxymethylated melamine and / or hexamethylenetetramine as a curing agent with respect to 100 parts by mass of the rubber component. A rubber composition and the conveyor belt of (8) or (9) above.

  The rubber composition for conveyor belts of the present invention is excellent in adhesiveness with a brass-plated steel cord, has a good vulcanization speed, and can produce a conveyor belt excellent in durability with high productivity.

It is a schematic sectional drawing which shows the test piece used for the adhesiveness test in an Example.

  As described above, the rubber composition for a conveyor belt of the present invention was added with 1 to 2 parts by mass of zinc dimethacrylate and 2 to 3.5 parts by mass of cobalt neodecanoate based on 100 parts by mass of the rubber component. It is characterized by this.

  As the rubber component constituting the rubber composition of the present invention, a known rubber can be used as an adhesive rubber layer of a steel cord in a conveyor belt. For example, natural rubber or a mixture of natural rubber and synthetic rubber can be used. .

  In this case, as the synthetic rubber, polyisoprene rubber (IR), polybutadiene rubber (BR), polychloroprene rubber and the like, which are homopolymers of conjugated diene compounds such as isoprene, butadiene, and chloroprene, the conjugated diene compound and styrene, Styrene butadiene copolymer rubber (SBR), vinyl pyridine butadiene styrene copolymer rubber, acrylonitrile butadiene copolymer, which are copolymers with vinyl compounds such as acrylonitrile, vinyl pyridine, acrylic acid, methacrylic acid, alkyl acrylates, alkyl methacrylates, etc. Rubber, butadiene acrylate copolymer rubber, butadiene copolymer methacrylate rubber, methyl acrylate butadiene copolymer rubber, methyl methacrylate butadiene copolymer rubber, ethylene, propylene, isobutyl Copolymers of olefins such as ethylene and diene compounds [eg, isobutylene isoprene copolymer rubber (IIR)], copolymers of olefins and non-conjugated dienes (EPDM) [eg, ethylene-propylene-cyclopentadiene ternary copolymer Polymers, ethylene-propylene-5-ethylidene-2-norbornene terpolymers, ethylene-propylene-1,4-hexadiene terpolymers], polyalkenamers obtained by ring-opening polymerization of cycloolefins (for example, Polypentenamer], rubber obtained by ring-opening polymerization of an oxirane ring (for example, polyepichlorohydrin rubber capable of sulfur vulcanization), polypropylene oxide rubber and the like. Further, halides of the above various rubbers such as chlorinated isobutylene isoprene copolymer rubber (Cl-IIR), brominated isobutylene isoprene copolymer rubber (Br-IIR) and the like are also included. Further, a ring-opening polymer of norbornene can be used. Furthermore, a saturated elastic body such as epichlorohydrin rubber, polypropylene oxide rubber, or chlorosulfonated polyethylene can be blended with the above-mentioned rubber. As the synthetic rubber, styrene butadiene copolymer rubber (SBR) is preferably used.

  The blending ratio of the natural rubber and the synthetic rubber is not particularly limited, but usually 20 to 50 parts by mass of natural rubber, 80 to 50 parts by mass of synthetic rubber, particularly 25 to natural rubber in 100 parts by mass of the rubber component. It is preferable to set it as -35 mass parts and synthetic rubber 75-65 mass parts.

  In the rubber composition for conveyor belts of the present invention, 1 to 2 parts by mass, preferably 0.5 to 2 parts by mass of zinc dimethacrylate is added to 100 parts by mass of the rubber component. The addition of this zinc dimethacrylate is intended to improve the adhesiveness with the brass-plated steel cord, and if the blending amount is less than 1 part by mass, a sufficient adhesive improvement effect cannot be obtained, and the present invention On the other hand, when the amount exceeds 2 parts by mass, the vulcanization rate is lowered, and the roll workability and treat workability are greatly reduced to lower the productivity, and the object of the present invention is also achieved. I can't. The term “roll processability” as used herein refers to the processability when kneading the rubber composition and passing it through a rolling roll to form a belt-like rubber having a predetermined thickness and width, and “treating workability” The workability of the process of bonding rubber rolled with a roll or the like and canvas.

  Moreover, in the rubber composition for conveyor belts of this invention, 2-3.5 mass parts of neodecanoic acid cobalt boride is added with respect to 100 mass parts of said rubber components, Preferably 2.5-3.5 mass parts is added. The addition of this neoborate cobalt borate can further improve the adhesive force, improve the vulcanization rate, and correct the decrease in the vulcanization rate due to the addition of zinc dimethacrylate. If the addition amount of the cobalt decanoate of neodecanoate is less than 2 parts by mass, the vulcanization rate may not necessarily be improved sufficiently, while if it exceeds 3.5 parts by mass, Adhesiveness decreases.

  Next, in this invention, a cobalt stearate can also be mix | blended with the said cobalt decanoate of a neodecanoate, and this can adjust the adhesiveness of a composition and can improve roll workability and treat workability | operativity. In this case, the compounding amount of cobalt stearate is not particularly limited, but usually 0.5 to 4 parts by mass, particularly 0.5 to 2 parts by mass with respect to 100 parts by mass of the rubber component. Is preferred. If the blending amount is less than 0.5 parts by mass, the effect of improving roll workability and treat workability by addition may not be sufficiently obtained, while if it exceeds 4 parts by mass, the adhesiveness may be lowered, In some cases, the rubber tack in the process of laminating the cover rubber is lowered and the laminating workability is lowered.

  An appropriate amount of a phenol resin can be blended in the rubber composition of the present invention for the purpose of further improving the adhesiveness. In this case, the phenol resin includes phenol-formaldehyde resin, resorcin-formaldehyde resin, cresol-formaldehyde resin and the like, and phenol-formaldehyde resin is particularly preferably used. In addition to 100% phenol resin, natural resin-modified phenol resin, oil-modified phenol resin, and the like can be used as the phenol resin. Here, although not particularly limited, those internally added with hexamethylenetetramine (hexamine), hexamethoxymethylated melamine (HMMM) and the like are preferably used because they further improve the adhesiveness. Phenol resins into which hexamethylenetetramine is added internally are preferably used.

  The blending amount of these phenol resins is not particularly limited, but is preferably 1 to 10 parts by mass, particularly 1 to 5 parts by mass with respect to 100 parts by mass of the rubber component. In this case, if the blending amount is less than 1 part by mass, a sufficient effect due to the addition may not be obtained. If the blending amount exceeds 10 parts by mass, the physical properties of the rubber deteriorate, adhesion to the kneader during rubber kneading, and roll workability. In some cases, it is not preferable in terms of a decrease in cost and an increase in cost. In addition, this phenol resin can also use 2 or more types together.

  In addition, for the purpose of further improving the adhesive force, a monocyclic aromatic compound containing a hydroxyl group such as resorcin and a polycyclic aromatic compound containing a hydroxyl group such as β-naphthol can be blended, In particular, β-naphthol is preferably used. The blending amount of β-naphthol and resorcin is not particularly limited, but is 1 to 10 parts by mass, particularly 1 to 5 parts by mass with respect to 100 parts by mass of the rubber component. If the blending amount is less than 1 part by mass, a sufficient effect due to the addition may not be obtained. On the other hand, if it exceeds 10 parts by mass, the physical properties of the rubber may be deteriorated or economically undesirable. Note that β-naphthol is preferably used in combination with hexamethoxymethylated melamine and / or hexamethylenetetramine, which will be described later.

  Furthermore, a hardening | curing agent can be mix | blended for the purpose of the improvement of adhesive force. Examples of the curing agent include methylene donors, and hexamethylenetetramine and methylolated melamine derivatives are preferably used. Examples of methylolated melamine derivatives include hexamethylolated melamine, hexamethoxymethylated melamine, and hexaethoxymethylated. Melamine, N, N ′, N ″ -trimethyl-N, N ′, N ″ -trimethylolated melamine, N, N ′, N ″ -trimethylolated melamine, N-methylolated melamine, N, N′-di (Methoxymethyl) melamine, N, N ′, N ″ -tributyl-N, N ′, N ″ -trimethylolated melamine and the like. Among these, hexamethoxymethylated melamine and / or hexamethylenetetramine are particularly preferable. The hexamethoxymethylated melamine and this are preferably used. / Or hexamethylenetetramine is preferably used in combination with the β- naphthol.

  Although the compounding quantity of a hardening | curing agent is not restrict | limited in particular, It is preferable to set it as 1-10 mass parts with respect to 100 mass parts of rubber components, especially 1-4 mass parts. If the blending amount is less than 1 part by mass, the effect due to the addition may not be sufficiently obtained. On the other hand, if it exceeds 10 parts by mass, the physical properties of the rubber may be deteriorated or economically undesirable.

  In the rubber composition of the present invention, sulfur, an organic sulfur compound, and other vulcanizing agents are usually used and are not particularly limited, but are usually 1 to 10 mass with respect to 100 mass parts of the rubber component. Part, preferably 2 to 5 parts by weight of vulcanizing agent. Although not particularly limited, vulcanization accelerating aids such as zinc white and stearic acid are added together with these vulcanizing agents in an amount of 1 to 20 parts by mass, preferably 3 to 15 parts per 100 parts by mass of the rubber component. A mass part can be mix | blended.

  The rubber composition of the present invention includes, for example, paraffinic, naphthenic, aromatic process oils, ethylene-α-olefin co-oligomers, paraffin wax, liquid paraffin and other mineral oils, castor oil, cottonseed oil, and sesame. Oils such as vegetable oils such as oil, rapeseed oil, soybean oil, palm oil, palm oil and peanut oil can also be blended, and aromatic process oil (aromatic oil) is particularly preferably used. Although the compounding quantity is not specifically limited, 1-10 mass parts with respect to 100 mass parts of rubber components, Preferably 2-7 mass parts can be mix | blended. Furthermore, a rubber composition can be prepared by adding an appropriate amount of fillers such as carbon black, silica, calcium carbonate, calcium sulfate, clay and mica according to the purpose and application, and carbon black is particularly preferably used.

  In the rubber composition of the present invention, various additives for rubber can be blended as necessary within a range that does not impair the object of the present invention. For example, vulcanization accelerators such as sulfenamides, anti-aging agents, waxes, antioxidants, foaming agents, plasticizers, lubricants, tackifiers, ultraviolet absorbers and the like can be appropriately contained.

  The rubber composition for conveyor belts of the present invention can be well adhered to a brass-plated steel cord by being placed and adhered onto a brass-plated steel cord and vulcanized. For example, a brass-plated steel cord can be bonded to the rubber composition of the present invention. The rubber composition can be bonded to and coated on the brass-plated steel cord by sandwiching with a sheet of the product, and heat-pressing the rubber composition to vulcanize and bond. In this case, the vulcanization conditions are appropriately selected according to the type of the vulcanizing agent and the vulcanization accelerator. For example, in the case of sulfur vulcanization, the conditions can be set at 135 to 180 ° C. for 10 to 100 minutes.

  The conveyor belt using the rubber composition of the present invention is not particularly limited. Usually, a core body coated with a brass-plated steel cord with an adhesive rubber layer made of the rubber composition of the present invention is covered with a cover rubber layer. It is assumed that it is arranged and adhered to. In this case, although not particularly limited, as such a conveyor belt, a lip guard belt in which a brass-plated steel cord is used as a breaker to prevent longitudinal tearing of the belt can be exemplified. In addition, the form of a brass plating steel cord, the rubber composition of a cover rubber layer, etc. can be suitably selected according to the use of a conveyor belt, etc., and can use a well-known thing.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not restrict | limited to the following Example. In addition, in the following example, a part and% show a mass part and mass%.

[Examples 1 to 10, Comparative Examples 1 to 13]
A rubber composition having the composition shown in Tables 1 and 2 below was prepared, and the adhesive strength with a brass-plated steel cord, vulcanization speed, treat workability, and laminating workability were evaluated by the following methods. The results are shown in Tables 1 and 2.

The details of each component shown in Tables 1 and 2 are as follows.
・ Natural rubber: RSS # 3
Styrene-butadiene rubber: SBR1500 (emulsion polymerization method SBR, manufactured by JSR)
・ Carbon black: Asahi Carbon Co., Ltd. “# 70”
・ Anti-aging agent: Sumitomo Chemical Co., Ltd. “ANTIGENE 6C”
Aroma oil: Idemitsu Kosan Co., Ltd. “Diana Process Oil AH-85”
・ Sulfur: Tsurumi Chemical Co., Ltd. “Z Sulfur”
・ Vulcanization accelerator: Ouchi Shinsei Chemical Co., Ltd. “Noxeller NS-F”
・ Zinc flower: Toho Zinc Co., Ltd.
・ Zinc dimethacrylate: Kawaguchi Chemical Industry Co., Ltd. “Actor ZMA”
・ Cobalt Neodecanoate: DIC Corporation “Cobaltic acid cobalt” (Net cobalt content 14.2%)
・ Cobalt borate of neodecanoate: DIC Corporation “DICNATE NBC-II” (22% net cobalt content)
・ Cobalt naphthenate: DIC Corporation “Cobalt naphthenate” (Net cobalt content 10%)
-Cobalt stearate: DIC Corporation "Cobalt stearate" (net cobalt content 9.5%)
・ Phenolic resin-1: Sumitomo Bakelite Co., Ltd. “Sumilite Resin PR-50235”
Phenol resin-2 (hexamethylenetetramine internal addition type): Sumitomo Bakelite Co., Ltd. “Sumilite Resin PR-12687”
・ Β-Naphthol: Mitsui Chemicals Fine Co., Ltd. “2-Naphthol”
・ Hexamethoxymethylated melamine: Nippon Cytec Industry “CYREZ964RPC”

(1) Adhesion test a. Preparation of Test Pieces Each component shown in Tables 1 and 2 was blended and kneaded using a Banbury mixer to obtain a rubber composition. A sheet of each rubber composition (thickness 15 mm) was prepared, and a brass-plated steel cord (diameter 7 mm) was sandwiched between a pair of sheets and subjected to pressure vulcanization at 170 ° C. for 40 minutes, and then tested. A piece was made.
b. Heat Aging Adhesive Strength After heating the above test piece under a pressure (2 MPa) with a pressure press at 145 ° C. for 300 minutes, a brass-plated steel cord was pulled out from each test piece, and the pulling force was measured. . In this case, the pull-out test was performed according to DIN 22131. Evaluation was indexed with the pulling force of Comparative Example 4 in Table 1 as 100. The higher the value, the larger and better the adhesive strength.

(2) Vulcanization speed The value of 155 ° C. and Tc (90) was measured by the method specified in JIS K6300-2. For measurement, “Charactometer W type” manufactured by Nichigo Corporation was used. The measurement value of Comparative Example 4 was set to 100, and the index was displayed so that the smaller the value of Tc (90), the larger the value.

(3) Treat workability Adjusting the calendar of the three calendars so that the rubber is rolled to a thickness of 1.5 mm, and rolling the rubber while throwing the canvas (thickness 0.8 mm, made of nylon) from the back, the canvas Is pulled out of the calendar and the canvas covered with rubber on one side is discharged. The workability at this time was evaluated as treat workability. The evaluation was made in three stages: good ◎, good ○, and poor ×.

(4) Lamination workability An unvulcanized rubber laminate formed in the form of the conveyor belt shown in Fig. 1 was prepared as a sample. Samples were prepared by first kneading a cover rubber composition having the following composition with a Banbury mixer. Using this cover rubber composition, cover rubber layers 1 and 1 having a thickness of 4 mm were prepared and shown in Tables 1 and 2. Further, a brass-plated steel cord 3 having a diameter of 4 mm is sandwiched between adhesive rubber layers 2 and 2 each having a thickness of 2 mm formed from each rubber composition, and further sandwiched between the pair of cover rubber layers 1 and 1, and a hand roller It was made to crimp by.

(Cover rubber composition)
Natural rubber (RSS # 3) 70 parts by mass Styrene butadiene rubber (SBR 1500, manufactured by JSR) 30 parts by mass HAF carbon 55 parts by mass Stearic acid (Kao Corporation “LUNAC RA”) 2 parts by mass ZnO 3 parts by mass Wax (large Inner Emerging Chemical Industry “Sannok N”) 2 parts by mass anti-aging agent RD (Kawaguchi Chemical “ANTAGE RD”) 0.5 parts by mass anti-aging agent 6C (Kawaguchi Chemical “ANTAGE 6C”) 0.5 parts by mass aroma oil (Idemitsu) Kosan Co., Ltd. “Diana Process Oil AH-85”) 5 parts by mass sulfur 2 parts by mass vulcanization accelerator (Ouchi Shinsei Chemical Co., Ltd. “Noxeller NS-F”) 0.7 parts by mass

Each of the obtained samples was forcibly peeled between the cover rubber layer / adhesive rubber layer, and the adhesiveness was evaluated by ◯ indicating that the adhesive strength was sufficient and Δ for the insufficient adhesive strength.

  As shown in Tables 1 and 2, the rubber composition for conveyor belts of the present invention has improved adhesion to the brass-plated steel cord without causing a delay in the vulcanization speed, and is excellent with the brass-plated steel cord. It has excellent adhesiveness and good vulcanization speed, and can produce a conveyor belt excellent in durability with high productivity.

1 Cover rubber layer 2 Adhesive rubber layer 3 Brass plated steel cord

Claims (9)

  A rubber composition for a conveyor belt, comprising 1 to 2 parts by mass of zinc dimethacrylate and 2 to 3.5 parts by mass of cobalt borate neodecanoate with respect to 100 parts by mass of the rubber component.   The rubber composition for a conveyor belt according to claim 1, wherein 20 to 50 parts by mass of natural rubber and 80 to 50 parts by mass of synthetic rubber are contained in 100 parts by mass of the rubber component.   The rubber composition for a conveyor belt according to claim 2, wherein the synthetic rubber is one or more selected from styrene-butadiene rubber (SBR), butadiene rubber (BR), and isoprene rubber (IR).   The rubber composition for conveyor belts of any one of Claims 1-3 which contain 1-10 mass parts of phenol resins with respect to 100 mass parts of rubber components.   The rubber composition for conveyor belts according to claim 4, wherein the phenolic resin is internally added with hexamethylenetetramine.   The rubber composition for conveyor belts according to any one of claims 1 to 5, wherein β-naphthol is contained in an amount of 1 to 10 parts by mass with respect to 100 parts by mass of the rubber component.   The rubber composition for conveyor belts according to any one of claims 1 to 6, comprising 1 to 10 parts by mass of hexamethoxymethylated melamine and / or hexamethylenetetramine as a curing agent with respect to 100 parts by mass of the rubber component. .   In the conveyor belt by which the brass plating steel cord coat | covered with the adhesive rubber layer was arrange | positioned as a core body between cover rubber layers, the said adhesive rubber layer is formed with the rubber composition of any one of Claims 1-7. Conveyor belt characterized by being made.   The conveyor belt according to claim 8, which is a lip guard type belt using a brass-plated steel cord as a breaker.

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