Foam layer manufacturing composition and foam rubber roller

Abstract

To provide a composition for manufacturing a foam layer of a foam rubber roller, and to provide a foam rubber roller having the foam layer.SOLUTION: A composition for manufacturing a foam layer comprises silicone rubber, water, a water-absorbing polymer, and a surfactant, and is characterized in that a weight ratio (X) of the water-absorbing polymer to the silicone rubber and a weight ratio (Y) of the surfactant to the silicone rubber satisfy the following conditions: 2.5 wt.%≤X≤20 wt.%, 0 wt.%<Y<2 wt.%. A foam rubber roller comprises a core material and a foam layer provided on the outer periphery of the core material, and is characterized in that the foam layer contains the silicone rubber, the water-absorbing polymer, and the surfactant, and that the weight ratio (X) of the water-absorbing polymer to the silicone rubber and the weight ratio (Y) of the surfactant to the silicone rubber satisfy the following conditions: 2.5 wt.%≤X≤20 wt.%, 0 wt.%<Y<2 wt.%.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a foam layer producing composition for producing a foam layer of a foam rubber roller, and a foam rubber roller provided with a foam layer. [Background technology]

[0002] 2. Description of the Related Art In electrophotographic image forming apparatuses such as copying machines and laser beam printers, a thermal fixing method is generally adopted as a method for fixing an unfixed toner image transferred onto a sheet of paper. In the thermal fixing method, a fixing roller that performs fixing and heating and a pressure roller that presses against the fixing roller are used, each of which has a rubber layer on the outer periphery of a core material such as aluminum or iron, and a release layer of fluororesin or the like on the surface of the rubber layer. In particular, in recent years, foam rubber rollers whose rubber layer is made of foam rubber with open cells have become popular in order to suppress changes in the surface hardness and outer diameter of the rubber layer.

[0003] Generally, methods for producing foamed rubber include (1) a method using a heated foaming agent, (2) a method using a hollow filler, and (3) an elution method. Of these, (1) the method using a heated foaming agent forms bubbles in the rubber by foaming the foaming agent during crosslinking. (2) The method using a hollow filler forms bubbles by dispersing the hollow filler in the rubber. (3) The elution method forms bubbles by dispersing a water-soluble powder in a rubber composition, curing the rubber, and then eluting the water-soluble powder. Patent Document 1 discloses (3) a method for manufacturing a rubber roller for thermal fixing using an elution method, in which sugar powder such as glucose or lactose is dispersed in a silicone rubber composition to cause primary curing, and after curing, the mold is immersed in water to cause the sugar powder to elute into the water, and after elution, the silicone rubber together with the core material is pulled out of the mold and subjected to secondary curing. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-8990 Summary of the Invention [Problem to be solved by the invention]

[0005] The sugar powder leaching method can produce uniform foamed rubber with a high open cell ratio, but the sugar precipitates from the water after leaching, which must be treated as industrial waste, resulting in high disposal costs.Furthermore, a step of immersing the foamed rubber roller in water to leach the sugar is required between the primary and secondary vulcanization, which increases the number of steps and leaves room for improvement in terms of production efficiency.

[0006] An object of the present invention is to provide a foam layer manufacturing composition that solves the above-mentioned problems, and a foam rubber roller that has a foam layer manufactured using the foaming composition and that ensures a quality level as a fixing roller, pressure roller, or conveying roller for an image forming apparatus. [Means for solving the problem]

[0007] The composition for producing a foam layer of the present invention comprises silicone rubber, water, a water-absorbing polymer, and a surfactant, and is characterized in that the weight ratio (X) of the water-absorbing polymer to the silicone rubber and the weight ratio (Y) of the surfactant each satisfy the following: 2.5wt%≦X≦20wt% 0wt% <Y<2wt%

[0008] In the foam layer manufacturing composition of the present invention, the weight ratio (X) of the water-absorbing polymer to the silicone rubber and the weight ratio (Y) of the surfactant may each satisfy the following. 5wt%≦X≦10wt% 0.25wt%≦Y≦0.75wt%

[0009] The foamed rubber roller of the present invention comprises a core material and a foamed layer disposed on the outer periphery of the core material, the foamed layer containing silicone rubber, a water-absorbing polymer, and a surfactant, and is characterized in that the weight ratio (X) of the water-absorbing polymer to the silicone rubber and the weight ratio (Y) of the surfactant respectively satisfy the following: 2.5wt%≦X≦20wt% 0wt% <Y<2wt%

[0010] In the foamed rubber roller of the present invention, the weight ratio (X) of the water-absorbing polymer and the weight ratio (Y) of the surfactant relative to the silicone rubber may each satisfy the following. 5wt%≦X≦10wt% 0.25wt%≦Y≦0.75wt% [Effects of the Invention]

[0011] The foam layer manufacturing composition of the present invention uses a water-absorbent polymer as a material for forming open cells, and thus the water evaporates simultaneously with the secondary vulcanization during the foam layer manufacturing process, eliminating the disposal costs associated with sugar powder as industrial waste. Furthermore, the foam layer can be manufactured in two steps, primary vulcanization and secondary vulcanization, without the need for an elution step in which the foam rubber roller is immersed in water, resulting in high manufacturing efficiency. Furthermore, by specifying the optimal range of the composition for manufacturing the foam layer, the properties and appearance of the foam layer can be improved, and a foam rubber roller can be obtained that can ensure the quality level required for a fixing roller, pressure roller, or conveying roller for an image forming device. [Brief explanation of the drawings]

[0012] [Figure 1] Foam rubber roller illustration DETAILED DESCRIPTION OF THE INVENTION

[0013] The foam layer manufacturing composition and foam rubber roller of the present invention will be described in detail below with reference to the drawings.

[0014] <1> Foam rubber roller Foam rubber roller A is a roller used in electrophotographic copiers, and is used as a fixing roller, pressure roller, or transport roller. Here, the "fixing roller" is a roller that applies heat to paper onto which toner has been transferred, fixing the toner to the paper. The "pressure roller" is a roller that pairs with the fixing roller and presses the paper against the fixing roller to adhere the toner to the paper. The "transport roller" is a roller that moves the paper within the device. The foam rubber roller A comprises a core A1 made of aluminum alloy, iron, stainless steel, etc., a foam layer A2 provided on the outer periphery of the core A1, and a release layer A3 covering the outer periphery of the foam layer A2 (Figure 1). The thickness of each layer varies depending on the use and specifications of the foam rubber roller A, but typically the foam layer A2 has a thickness of about 1 to 10 mm, and the release layer A3 has a thickness of about 10 to 100 μm. When the foam rubber roller A is a transport roller, the release layer A3 is not an essential component.

[0015] <2> Composition for producing foam layer The foam layer producing composition 1 is a composition for producing the foam layer A2. The foam layer manufacturing composition 1 comprises at least silicone rubber 10, water 20, water-absorbing polymer 30, and surfactant 40, and is liquid at room temperature. The foam layer-producing composition 1 is cured by vulcanization according to a predetermined procedure to form the foam layer A2 of the foam rubber roller A. The formulation of the foam layer manufacturing composition 1 satisfies at least the following formulas in terms of the weight ratio (X) of the water-absorbing polymer 30 to the silicone rubber 10 and the weight ratio (Y) of the surfactant 40 to the silicone rubber 10. With this formulation, the foam layer A2 at least meets the performance requirements of the conveying roller.

[0016]

number

[0017] More preferably, (X) and (Y) each satisfy the following formula: With this blending, the foam layer A2 further satisfies the performance requirements of the fixing roller and pressure roller.

[0018]

number

[0019] <2.1> Examples of materials for the composition for manufacturing the foam layer Examples of the silicone rubber 10 that can be used include addition reaction liquid silicone rubber that hardens through an addition reaction of a platinum catalyst, condensation reaction liquid silicone rubber that hardens through a condensation reaction, and organic peroxide liquid silicone rubber that hardens through a peroxidation reaction. The silicone rubber 10 may also contain a reinforcing filler such as carbon black, silica, or calcium carbonate as a reinforcing material. The water 20 may be ion-exchanged water, distilled water, tap water, well water, or the like. For example, acrylic acid, methacrylic acid, alkali metal salt polymers thereof, copolymers thereof, or crosslinked bodies thereof can be used as the water-absorbing polymer 30. The particle size of the water-absorbing polymer 30 is preferably about 20 μm to 50 μm in median particle size. As the surfactant 40, for example, sorbitan monooleate, sorbitan trioleate in sorbitan fatty acid ester, other glycerin fatty acid ester, polyoxyethylene sorbitan fatty acid ester, or various monooleates, diolates, or triolates in polyoxysorbitol fatty acid ester can be used.

[0020] <3> release layer The release layer A3 is a layer for improving the releasability from the toner, and may be configured as a tube structure that covers the outer periphery of the foam layer A2. The release layer A3 may be made of, for example, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), polyvinylidene fluoride (PVdF), etc. Also, instead of fluororesin, polyimide resin, polyamide-imide resin, etc. may be used. It is desirable to previously roughen the inner surface of the tube of the release layer A3 by etching.

[0021] <4> Manufacturing method of foam rubber roller When the foamed rubber roller A is a fixing roller, the foamed rubber roller A is manufactured by, for example, the following method.

[0022] <4.1> Setting the mold A cylindrical mold is set upright, the bottom of which is sealed with a bottom plate having an injection hole, a fluororesin tube that will form the release layer A3 is inserted into the mold, and the core material A1 is set upright and fixed in the center of the fluororesin tube. It is desirable to coat the outer surface of the core material A1 and the inner surface of the fluororesin tube with a primer.

[0023] <4.2> Primary vulcanization A predetermined blend of foam layer manufacturing composition 1 is injected into the space between the fluororesin tube and the core material A1 in the mold through the injection hole in the bottom plate, and the top of the mold is sealed with a lid to carry out primary vulcanization. The vulcanization temperature is preferably 80°C to 90°C, and the vulcanization time is preferably about 50 to 80 minutes. By primary vulcanization, the foam layer manufacturing composition 1 is thermally cured, and a silicone rubber cured body is formed between the core material A1 and the release layer A3, with the water-retaining water-absorbent polymer 30 dispersed therein.

[0024] <4.3> Post-vulcanization The cured silicone rubber and release layer A3 are removed from the mold together with the core A1, and then secondary vulcanization is carried out. The vulcanization temperature is preferably 160°C to 230°C, and the vulcanization time is preferably about 4 to 6 hours. The secondary vulcanization stabilizes the physical properties of the silicone rubber 10, and simultaneously volatilizes the water in the water-absorbent polymer 30, forming fine interconnected cells within the cured silicone rubber. Through the above steps, a three-layer foamed rubber roller A can be obtained, in which a silicone rubber foam layer A2 and a fluororesin release layer A3 are laminated in this order on a core A1. If the foamed rubber roller A is a conveying roller without the release layer A3, the same manufacturing steps are carried out except for the fluororesin tube.

[0025] <5> Comparison Test In order to manufacture a foamed rubber roller suitable as a fixing roller, pressure roller, or conveying roller for an image forming apparatus, test pieces of a foamed layer were manufactured using compositions for manufacturing a foamed layer with various blends, and comparative tests were conducted on the physical properties and appearance of the test pieces. [Silicone Rubber] Addition reaction type liquid silicone rubber [Water-absorbent polymer] Partially sodium salt-crosslinked acrylic acid polymer ("Sunfresh (registered trademark) ST-500MPSA" manufactured by Sanyo Chemical Industries, Ltd.) [Water] Ion-exchanged water [Surfactant 1] Sorbitan monooleate ("Rheodor (registered trademark) SP-O10V" manufactured by Kao Corporation) [Surfactant 2] Sorbitan trioleate (Kao Corporation "Rheodor SP-O30V") [Primary vulcanization] Vulcanization temperature: 90°C Vulcanization time: 80 minutes [Secondary vulcanization] Vulcanization temperature: 230°C Vulcanization time: 5 hours [Evaluation method] JIS k 6249 [Test piece] Cylinder (diameter 29.0±0.5mm, height 12.5±0.5mm) [Physical properties] Compression set (%), specific gravity (g / cm 3 ), water absorption rate (%) [Appearance] Finish of test piece cross section ○: Dent amount at the edge and center of the test piece cross section is less than 1.5% △: Dent amount at the edge and center of the test piece cross section is 1.5% or more but less than 3% ×: Dent amount at the edge and center of the cross section of the test piece is 3% or more

[0026] <5.1> Required performance of conveyor rollers The transport rollers used in electrophotographic copiers transport a large number of sheets of paper continuously at high speed, so if the surface of the foam layer is uneven, when the paper comes into contact with the surface, the contact resistance will be different from that of other parts, causing uneven transport and potentially resulting in uneven printing. For this reason, it is desirable that the foam layer for the transport roller has a flat surface with only slight irregularities. Specifically, it is desirable that the amount of depression at the edges and center of the test piece is less than 1.5%.

[0027] <5.2> Required performance of fixing roller and pressure roller The fixing roller and pressure roller used in electrophotographic copiers work as a pair to sandwich paper and transport it at high speed. Therefore, if the compression set of the foam layer is large, the contact width (nip width) between the fixing roller and pressure roller will fluctuate, which may result in uneven fixing and affect print quality. For this reason, it is desirable that the foam layers of the fixing roller and pressure roller have a flat surface as well as good (low) compression set. Specifically, it is desirable that the amount of depression at the edges and center of the test specimen is less than 1.5% and that the compression set is 30% or less.

[0028] <6> Test results The test results of the comparison test are shown in Tables 1 and 2 below.

[0029] [Table 1]

[0030] [Table 2]

[0031] <7.1>Examples 8 to 14 Examples 8 to 14 are composed of formulations in which the weight ratio (X) of the water-absorbent polymer to the silicone rubber in the composition for producing the foamed layer satisfies 2.5 wt% ≤ X ≤ 20 wt%, and the weight ratio (Y) of the surfactant to the silicone rubber satisfies 0 wt% < Y < 2 wt%. In all of Examples 8 to 14, "○" (the amount of indentation at the end and the center of the test piece cross-section is less than 1.5%) was achieved in terms of appearance. From the above, Examples 8 to 14 satisfy at least the performance requirements as a conveyance roller for an electrophotographic copying machine.

[0032] <7.2>Examples 1 to 7 Examples 1 to 7 are composed of formulations in which the weight ratio (X) of the water-absorbent polymer to the silicone rubber in the composition for producing the foamed layer satisfies 5 wt% ≤ X ≤ 10 wt%, and the weight ratio (Y) of the surfactant to the silicone rubber satisfies 0.25 wt% < Y ≤ 0.75 wt%. In all of Examples 1 to 7, "○" (the amount of indentation at the end and the center of the test piece cross-section is less than 1.5%) was achieved in terms of appearance, and a permanent compression ratio of 30% or less was achieved. From the above, Examples 1 to 7 satisfy the performance requirements as a fixing roller, a pressure roller, and a conveyance roller for an electrophotographic copying machine. Regardless of monooleate and trioleate, the formulation of an excessive surfactant diffuses the surfactant not only at the interface between water + water-absorbent polymer and silicone rubber but also into the silicone rubber, and there is a risk of increasing the compression set by the residual surfactant in the silicone rubber after vulcanization. Similarly, if the water-absorbent polymer is excessively formulated, the excess water-absorbent polymer may have an adverse effect on the silicone rubber and increase the compression set. In Examples 1 to 7, it is presumed that the permanent compression ratio could be dramatically reduced by limiting and optimizing the weight ratio (X) of the water-absorbent polymer to the silicone rubber and the weight ratio (Y) of the surfactant to a better range than in Examples 8 to 14.

[0033] <7.3>Comparative Examples 1 to 4 In Comparative Examples 1 and 2, while the weight ratio (Y) of the surfactant to the silicone rubber satisfies 0 wt% < Y < 2 wt%, the weight ratio (X) of the water-absorbing polymer to the silicone rubber is 0.5 wt% and 1 wt% respectively, not satisfying the lower limit of 2.5 wt% ≤ X. As a result, the appearance is "×" (the dent amount at the end and the center of the test piece cross-section is 3% or more) and "△" (the dent amount at the end and the center of the test piece cross-section is more than 1.5% and less than 3%) respectively, not meeting the quality level as a foamed roller for an electrophotographic copying machine. In Comparative Examples 3 and 4, while the weight ratio (X) of the water-absorbing polymer to the silicone rubber satisfies 2.5 wt% ≤ X ≤ 20 wt%, the weight ratio (Y) of the surfactant to the silicone rubber is 0 wt% in both cases, not satisfying the lower limit of 0 wt% < Y. As a result, the appearance is "△" (the dent amount at the end and the center of the test piece cross-section is more than 1.5% and less than 3%) in both cases, not meeting the quality level as a foamed roller for an electrophotographic copying machine.

Explanation of Symbols

[0034] ​​​​​​​​​​​​​​​​​​

Claims

1. A composition for producing a foam layer in a foam rubber roller having a core material and a foam layer provided on the outer periphery of the core material, comprising: The composition comprises silicone rubber, water, a water-absorbing polymer, and a surfactant; The weight ratio (X) of the water-absorbing polymer to the silicone rubber and the weight ratio (Y) of the surfactant to the silicone rubber satisfy the following: composition. 2.5wt%≦X≦20wt% 0wt%<Y<2wt%

2. 2. The composition for producing a foam layer according to claim 1, The weight ratio (X) of the water-absorbing polymer to the silicone rubber and the weight ratio (Y) of the surfactant to the silicone rubber satisfy the following: composition. 5wt%≦X≦10wt% 0.25wt%≦Y≦0.75wt%

3. A foam rubber roller comprising a core material and a foam layer provided on the outer periphery of the core material, the foam layer comprises a silicone rubber, a water-absorbing polymer, and a surfactant; The weight ratio (X) of the water-absorbing polymer to the silicone rubber and the weight ratio (Y) of the surfactant to the silicone rubber satisfy the following: Foam rubber roller. 2.5wt%≦X≦20wt% 0wt%<Y<2wt%

4. 4. The foamed rubber roller according to claim 3, The weight ratio (X) of the water-absorbing polymer to the silicone rubber and the weight ratio (Y) of the surfactant to the silicone rubber satisfy the following: Foam rubber roller. 5wt%≦X≦10wt% 0.25wt%≦Y≦0.75wt%

Images