CN110205007B - Surface treatment coating for charging roller made of foaming material and preparation method thereof - Google Patents

Abstract

The invention discloses a surface treatment coating for a charging roller made of a foaming material and a preparation method thereof. The surface treatment coating for the charging roller made of the foaming material is prepared by mixing the following raw materials in percentage by weight: 72-89% of water-based polyurethane resin, 10-25% of filler particles, 0.5-1.5% of water-based resin thickener and 0.5-1.5% of paint wetting and leveling agent. The surface treatment coating provided by the invention is easy to attach to the surface of the PE foaming roller, can effectively cover holes on the surface, and provides a smooth surface for the PE foaming roller. And the transfer printing shaft of the laser printer, which has strong controllability, soft quality, wear resistance and low price, can be produced by matching with the existing water-based conductive coating of the transfer printing shaft of the charging roller.

Description

Surface treatment coating for charging roller made of foaming material and preparation method thereof

Technical Field

The present invention relates to a surface treatment coating for a charging roller made of a novel foam material used in an electrostatic recording device such as a laser printer, and particularly to a surface treatment coating using a water-based conductive coating as a roller shaft and a method for producing the same.

Background

Because the charging roller shaft used by the existing laser printer and other equipment has complex production process and large workshop occupied area. The method needs multi-step processes of mixing, molding, vulcanization, foaming, thermal stabilization, grinding and the like, has high cost and is difficult to realize full automation of production. In addition, many common additives for improving the performance of the charging roller, such as a plasticizer for decreasing hardness, conductive carbon black for increasing conductivity, and the like, are difficult to apply to rubber, and cause such phenomena as staining of the photosensitive drum caused by floating and gathering of organic volatiles, increase in hardness and increase in abrasion. Therefore, there is a need in the market for a new type of charging roller that can be used as a substitute for the rubber conductive roller. The roller produced by using the foamed Polyethylene (PE) has the advantages of low price, simple process, soft texture and the like, and has good commercial prospect. However, the charging roller cannot be directly used for laser printing because the hole structure on the surface of the PE foaming roller can absorb and adhere toner and conductive coating. As shown in fig. 1, the surface of the PE foam charging roller as a substrate is densely covered with 10-200 μm fine pores, and if the existing aqueous ultra-low VOC conductive coating is directly used for spraying, the pores absorb the coating to cause defects, so that the existing transfer shaft conductive coating cannot be directly applied to the surface.

Therefore, how to overcome the problem that the surface of the PE foaming roller is easy to absorb and stick toner is a problem to be solved in the industry that a smooth surface is provided so that the PE foaming roller can be directly used for laser printing.

Disclosure of Invention

The invention aims to solve the technical problems that the surface of a PE foaming roller is easy to absorb and adhere toner and is inconvenient to be directly used for laser printing, and provides a surface treatment coating which can effectively cover holes on the surface of the PE foaming roller and can be matched with the existing water-based charging roller conductive coating to produce a foaming material charging roller with strong controllability, softness, wear resistance and low price and a preparation method thereof.

The invention provides a surface treatment coating for a charging roller made of a foaming material, which is prepared by mixing the following raw materials in percentage by weight: 72-89% of water-based polyurethane resin, 10-25% of filler particles, 0.5-1.5% of water-based resin thickener and 0.5-1.5% of paint wetting and leveling agent.

Preferably, the aqueous polyurethane resin is aliphatic polyurethane with solid content of 40-45% and tensile rate of not less than 400%.

Preferably, the filler is diatomite or ground calcium carbonate, and the particle size of the filler is 400-800 meshes.

Preferably, the viscosity of the thickener should be 30-35s on a paint-4 cup basis.

The invention also provides a preparation method of the surface treatment coating for the charging roller made of the foam material, which comprises the following preparation steps:

step 1: weighing the weight of each raw material according to the proportion of the surface treatment coating of the charging roller, adding the coating wetting and leveling agent into the waterborne polyurethane resin, and stirring until the components are uniformly dispersed to prepare a first mixed solution;

step 2: adding the filler particles into the first mixed solution one by one, stirring at a stirring paddle speed of 500RPM, and stirring for 30 minutes after the filler particles are added to prepare a second mixed solution;

and step 3: and adding the aqueous resin thickener into the second mixed solution for thickening, stirring at a speed of 500RPM, and adjusting the viscosity to be 30-35s based on a coating-4 cup.

The surface treatment coating provided by the invention is a water-based resin coating, is easy to attach to the surface of a PE foaming roller, can effectively cover holes on the surface, and provides a smooth surface for a cheap foaming charging roller. So that the transfer shaft coating sprayed on the surface of the roller is conductive and does not contaminate the photosensitive drum, which is essentially to treat the surface of the foamed polyethylene roller, i.e., to coat the roller with a film so that the transfer shaft coating can be sprayed on the new surface of the roller without causing defects. The conductive coating can be matched with the existing water-based conductive coating of the transfer printing shaft of the charging roller, and further can be used as the transfer printing shaft (charging roller) of a laser printer with strong controllability, soft quality, wear resistance and low price.

Drawings

FIG. 1 is an enlarged schematic view of the surface of a PE foam charging roller;

FIG. 2 is an enlarged schematic view of the surface of a PE foamed charging roller dip-coated with the surface treatment coating of the present invention;

FIG. 3 is an enlarged schematic view of the PE foam charging roller of FIG. 2 after being coated with a transfer shaft coating;

fig. 4 is a schematic diagram of the results of the printing test on the machine using the PE foam charging roller shown in fig. 3.

Detailed Description

The invention is further illustrated in the following description with reference to the figures and examples:

the invention provides a surface treatment coating for a charging roller made of a foaming material, which is prepared by mixing the following raw materials in percentage by weight: 72-89% of water-based polyurethane resin (PUD), 10-25% of filler particles, 0.5-1.5% of water-based resin thickener and 0.5-1.5% of paint wetting and leveling agent.

Among them, the aqueous polyurethane is used as a film-forming substrate because it has properties such as: very low content of volatile organic matter, easy mixing with additive, no gel, high stretching rate, high wear resistance and other advantages. The controllable range of the viscosity is optimal when the solid content is 40-45%. The aliphatic polyurethane has low film-forming hardness, good film-forming rate and elongation not less than 400%. If the solids content is too low, then the amount of thickener to be added is large, leading to increased costs and susceptibility to uncontrolled defects. Certainly, when the solid content is too high, the solid content can be automatically diluted by using solvents such as deionized water and the like.

The filler is common high-mesh (mesh is more than or equal to 500) diatomite or ground calcium carbonate and the like on the market and is used for increasing the adhesive force of the coating and reducing the shrinkage of the PUD. The diatomite can greatly increase the adsorption effect of the coating on the charging roller body and physical characteristics such as compression resistance, wear resistance and the like, and the polyurethane film is not easy to fall off and damage. After the diatomite is added, the smoothness of the surface of the charging roller is greatly improved, and the adhesive force and the wear resistance of the surface of the pore space are improved. The filler has a particle size of 400-800 mesh (38-18 μm) and is preferably used for adsorbing pores. However, when the amount is more than 25%, the hardness of the charging roller becomes high and the elongation of the polyurethane film is lowered. The addition amount of the additive is 10-25% after multiple tests by a team.

The thickener is used to adjust the viscosity of the PUD, suitably on a coat-4 cup basis for 30-35 s. The phenomena of uneven adhesion such as shrinkage cavity and the like easily occur due to too low viscosity, the defective rate is high, the phenomena of long drying time, uneven drying and resin accumulation at two ends easily occur due to too high viscosity, and extra steps for cleaning are needed.

The paint wetting and leveling agent is added to wet the porous surface of the foamed PE material, the addition amount is not less than 0.5 percent, and the paint wetting and leveling agent is used for ensuring that a formed film is smooth during drying and no bubble mark exists after drying. The paint wetting and leveling agent can effectively overcome the higher surface tension of an aqueous solvent. Generally, when the surface tension of the coating is reduced to 25 mN/m, no craters occur during the drying process. Because the pores of different foaming PE materials are different in size, the usage amount can be increased according to needs. The viscosity of the coating is kept at a high level corresponding to the surface tension to ensure the film thickness, and the wetting and leveling agent is matched to avoid the problem of shrinkage cavity. The viscosity was best between 30-35 seconds as measured by viscosity cup (paint-4 cup). If the viscosity is too low, the film-forming thickness is low, the processing difficulty is greatly increased, and the finished product is easy to damage. Therefore, a thickener is required to secure a film thickness, and the amount of the present invention is controlled in the range of 0.5% to 1.5%.

According to actual needs, different raw material proportions can be selected to prepare the foamed charging roller surface treatment coating, as shown in the following table, but the foamed charging roller surface treatment coating is not limited to the following raw material proportions:

the surface treatment coating of the charging roller made of the foaming material can be prepared according to the following steps by selecting a raw material ratio, and the preparation steps are as follows:

step 1: weighing the weight of each raw material according to the proportion of the selected surface treatment coating of the charging roller made of the foaming material, adding the coating wetting and leveling agent into the waterborne polyurethane resin, and stirring until the coating wetting and leveling agent is uniformly dispersed to prepare a first mixed solution;

step 2: adding filler particles into the first mixed solution for multiple times, stirring at a stirring paddle speed of 500RPM, and stirring for 30 minutes after the filler particles are added to obtain a second mixed solution;

and step 3: and adding the water-based resin thickener into the second mixed solution for thickening, stirring at the speed of 500RPM, and adjusting the viscosity to be 30-35s based on a coating-4 cup to obtain the surface treatment coating of the foaming material charging roller.

The surface treatment coating for the charging roller made of the foaming material prepared according to the mixture ratio of the four embodiments is detected:

the prepared foaming material charging roller is slowly inserted into the surface treatment coating of the foaming material charging roller for dip-coating, after effusion at two ends is removed, the roller is dried under the environment of 75 ℃ and tested, and the test result is as follows:

1. the charging roller prepared by dip coating of the four examples has smooth and flat surface, no holes and no bubble marks.

2. The adhesion force of the polyurethane film to the surface of the charging roller prepared by dip coating in the four embodiments is larger than the strength of the foamed PE, namely, the surface film of the charging roller still cannot fall off under the condition that the foamed PE is about to break due to external force.

3. After the charging roller prepared by dip-coating in the four embodiments uses the conductive coating on the surface, the wettability of the conductive coating on the surface is good, and the phenomena of shrinkage cavity and the like do not exist. The rolling is carried out for a long time, and the extrusion does not crack or delaminate.

From the above three points, the surface coating can effectively cover the surface of the foamed PE with rich pores and is used as an excellent carrier of the conductive coating of the charging roller. As shown in fig. 1, the PE foam charging roller as a substrate has fine pores densely distributed on the surface thereof, so that the conventional conductive coating for transfer shaft cannot be directly applied to the surface thereof. As shown in FIG. 2, the PE foaming charging roller dipped with the surface treatment coating provided by the invention effectively covers the pores on the surface of the charging roller, can effectively cover the pores after film forming, and has the advantages of high film forming elongation, strong adhesive force and smooth and flat surface. Particularly, after the filler particles are added, the surface smoothness of the charging roller is greatly improved, the adhesive force and the wear resistance of the surface of the pore are improved, and the precision requirement of the charging roller of the laser printer can be well met, as shown in fig. 3 and 4.

The surface treatment coating for the charging roller made of the foaming material fills the gap of the commercial application of the charging roller using the foaming PE as the base material, and can effectively reduce the part cost of recording equipment such as a laser printer and the like which needs to use the charging roller. The invention has the advantages of easy preparation and simple process, and has good binding force on the surfaces of the waterborne conductive coating and the foamed PE. Good ductility, wear resistance and tearing resistance.

While the present invention has been described in detail with reference to the embodiments, those skilled in the art may make various changes or modifications to the embodiments, and such changes and modifications should fall within the scope of the present invention.

Claims (2)

1. The surface treatment coating for the foamed polyethylene charging roller is characterized by being easily attached to the surface of the foamed polyethylene charging roller, effectively covering holes on the surface and being used as a carrier of a conductive coating of the charging roller; the surface treatment coating is prepared by mixing the following raw materials in percentage by weight: 72-89% of water-based polyurethane resin, 10-25% of filler particles, 0.5-1.5% of water-based resin thickener and 0.5-1.5% of paint wetting and leveling agent;

the aqueous polyurethane resin is aliphatic polyurethane with solid content of 40-45% and tensile rate not less than 400%;

the filler is diatomite or ground calcium carbonate, and the particle size of the filler is 400-800 meshes;

the viscosity of the thickening agent is 30-35s on a coating-4 cup basis;

and after the foamed polyethylene charging roller is inserted into the surface treatment coating for dip coating, removing effusion at two ends, so that the foamed polyethylene charging roller is coated with a layer of film of the surface treatment coating.

2. A method for preparing a surface treatment coating of the foamed polyethylene charging roller according to claim 1, which comprises the following steps:

step 1: weighing the weight of each raw material according to the proportion of the surface treatment coating of the foamed polyethylene charging roller, adding the coating wetting and leveling agent into the waterborne polyurethane resin, and stirring until the coating wetting and leveling agent is uniformly dispersed to prepare a first mixed solution;

step 2: adding the filler particles into the first mixed solution one by one, stirring at a stirring paddle speed of 500RPM, and stirring for 30 minutes after the filler particles are added to prepare a second mixed solution;

and step 3: and adding the aqueous resin thickener into the second mixed solution for thickening, stirring at a speed of 500RPM, and adjusting the viscosity to be 30-35s based on a coating-4 cup.

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