JPH0136844B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a low-hardness polyurethane molded product that has non-bleeding properties. Conventionally, a roll made of softened polyurethane with low hardness has been used as a paper feed roll in an electrophotographic copying machine. Rolls made of such softened polyurethane have excellent mechanical properties such as abrasion resistance, but they also contain oils and plasticizers such as dioctyl phthalate, dioctyl adipate, or dipropylene glycol dibenzoate. , softened to have appropriate hardness. As a result, conventional paper feed rolls made of polyurethane containing these plasticizers have a problem of poor toner resistance. In other words, a so-called bleeding phenomenon occurs in which plasticizer and oil ooze out onto the roll surface over time, and the oozing plasticizer and oil dissolve the resin that makes up the toner, causing the roll surface to bleed while the copying machine is in use. Toner sticks and accumulates on
This reduces paper feeding performance. Furthermore, if bleeding occurs in the paper feed roll, it can also contaminate the copy paper. In addition, the temperature inside an electrophotographic copying machine is often 10 to 20 degrees Celsius higher than the environmental temperature when the machine is used, and therefore the paper feed roll has a temperature of around 0 degrees Celsius to 50 degrees Celsius.
Constant paper feeding performance is required over a wide temperature range that includes nearby high temperatures, but paper feeding rolls made of softened polyurethane such as those described above do not have sufficient temperature stability and are difficult to use when used at high temperatures. The adhesion of toner to the paper feed roll and the reduction in the coefficient of friction of the surface required for the paper feed roll become more pronounced. Furthermore, the above-mentioned bleeding of plasticizer onto the roll surface is not only undesirable in paper feed rolls for copiers, but also generally in printing rolls,
Squeegees for screen printing, silicon wafer transport rolls in the manufacture of integrated circuit chips, etc. also cause various undesirable problems. The present invention was made in order to solve the problem of plasticizer bleeding in rolls generally made of conventional polyurethane, and the present invention substantially eliminates the problem of plasticizer bleeding in rolls made of conventional polyurethane. It is an object of the present invention to provide a method for producing a polyurethane molded product that maintains a coefficient of friction and has excellent temperature stability at high temperatures. Therefore, the present invention also provides a method for producing a paper feed roll for an electrophotographic copying machine that has excellent toner resistance, maintains a required coefficient of friction, and has constant paper feeding performance even under high temperatures inside the copying machine. It is an object of the present invention to provide a method for manufacturing a non-bleeding polyurethane molding that is particularly suitable for. The method of the present invention uses a urethane prepolymer obtained by reacting a polyol and a polyisocyanate.
A composition consisting of 30 to 100 parts by weight of a reactive oligomer having two or more hydroxyl groups in the molecule and an average molecular weight of 2000 to 3000 and 2 to 8 parts by weight of a curing agent per 100 parts by weight. A non-bleeding, low-hardness polyurethane molded product having a hardness of 10 to 60 degrees is produced by curing and molding under heating. The urethane prepolymers used in the present invention are preferably obtained by reaction of polyols such as polyester polyols or polyether polyols with polyisocyanates according to conventional methods. Such urethane prepolymers are commercially available. Examples of the polyol include one or a mixture of two or more glycols such as ethylene glycol, butylene glycol, diethylene glycol, 1,5-pentanediol, 1,3-hexanediol, or neopentyl glycol, and adipic acid, etc. Polyester polyols such as polyester polyols obtained by reacting with dicarboxylic acids having 2 to 6 carbon atoms, polycarbonate ester polyols, polycaprolactone ester polyols obtained by ring-opening polymerization of caprolactone, and polyoxymethylene glycols. , polyether polyols such as polyoxypropylene glycol are preferably used. In addition, as the polyisocyanate, tolylene diisocyanate, diphenylmethane-4,
4'-diisocyanate, naphthalene-1,5-diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate and the like are preferably used. However, the polyol and polyisocyanate in the polyurethane prepolymer used in the present invention are not limited to the above. As mentioned above, in order to use a roll made of polyurethane as a paper feed roll, the polyurethane must be softened, and therefore the composition for polyurethane moldings must contain a plasticizer. It is. Here, the composition used in the method of the present invention contains, as a plasticizer, a reactive oligomer having two or more hydroxyl groups in the molecule and having an average molecular weight of 500 to 3,000. Such a reactive oligomer has 2 in its molecule.
Because the urethane prepolymer molecules are chemically bonded to the urethane prepolymer molecules by three or more hydroxyl groups during crosslinking and curing, no bleeding occurs on the surface after molding, and the molecules have a high molecular weight and long length. Because of the presence of the chains, a certain distance is maintained between the urethane prepolymer molecules via the crosslinked chains, thus making it possible to soften the polyurethane after molding. Examples of the above-mentioned reactive oligomers include polyols such as polyester polyols and polyether polyols, liquid polybutadiene rubber, and silicone rubber. Preferred specific examples include, for example, organic acids such as polyethylene adipate, and polyols such as polyester polyols and polyether polyols. Examples include condensates of alcohols, ring-opening polymers such as caprolactone esters and polyoxyethylene glycol, and liquid rubbers such as silicone and butadiene rubbers. However, it is not limited to these. In the method of the present invention, the reactive oligomer has an average molecular weight in the range of 500 to 3000, and the urethane prepolymer is It is preferable to contain 10 to 100 parts by weight of the above-mentioned reactive oligomer per 100 parts by weight. When the amount of the reactive oligomer is outside this range, it is possible to impart the appropriate hardness necessary to impart the required performance to a molded article, such as a paper feed roll for an electrophotographic copying machine or a squeegee for screen printing. Because you can't. The polyurethane molding composition used in the present invention further contains a curing agent. Its blending amount is
It is selected as appropriate depending on the application of the molded product, but for example, in order to make it soft enough to be used as the above-mentioned paper feed roll or squeegee, 2 to 8 parts by weight of the curing agent should be added to 100 parts by weight of the urethane prepolymer. It is preferable to mix 1 part. Specific examples of curing agents used include 4,4-methylenebis(2-chloroaniline), triisopropanolamine, ethylene glycol, 1,4-butanediol,
2,3-butanediol, 1,1,1-trimethylolpropane, 3,3'-dichloro-4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, and hydroquinone-bis(β -hydroxylethyl) ether alone or in mixtures. The composition for a polyurethane molded article described above can be processed into a desired molded article by a conventional method known in the production of polyurethane molded articles. For example, to manufacture paper feed rolls for electrophotographic copying machines, a mixture consisting of a urethane prepolymer, the aforementioned reactive oligomer, and a curing agent is poured into a predetermined mold heated to about 100°C, heated for several hours, and then molded. Take it out and heat it with heated air at 90℃ for 10 minutes.
All you have to do is bake it for about an hour or so. The polyurethane molded product obtained in this way,
For example, paper feed rolls for electrophotographic copying machines do not bleed not only at room temperature but also at high temperatures around 50°C, and therefore have good toner resistance without toner sticking to the roll surface due to bleeding. The friction coefficient does not substantially decrease over a long period of time even after 200 days at room temperature or under severe conditions due to temperature changes of -10 to 60°C. As described above, according to the method of the present invention, since a composition for polyurethane moldings containing a high molecular weight and reactive oligomer as a plasticizer is used, non-bleeding property is required. Various soft and low hardness polyurethane molded products can be obtained. For example, as mentioned above, in addition to paper feed rolls for electrophotographic copying machines with good toner resistance,
The company manufactures printing rolls, squeegees for screen printing, and rolls for transporting silicon wafers for manufacturing integrated circuit chips. Examples are shown below, but the present invention is not limited to these Examples. In the following examples, a paper feed roll for an electrophotographic copying machine was molded using a composition for a polyurethane molded product, and when the paper feed roll had a composition according to the present invention, it was considered as an invention product.
The product using the conventional composition is referred to as a comparative product. In addition, parts indicate parts by weight. Example (1) Invention 1 100 parts of urethane polymer (Takenate L1270 manufactured by Takeda Pharmaceutical Co., Ltd.), polyethylene adipate (0DX manufactured by Dainippon Ink and Chemicals Co., Ltd.) with an average molecular weight of 2000 and a hydroxyl value of 55 as a reactive oligomer 102) 50
and 4,4-methylenebis(2
-Chloroaniline) and triisopropanolamine (3:7 molar ratio) were mixed, and 100
After pouring into a mold heated to .degree. C. and heating, it was taken out from the mold and baked in heated air at 90.degree. C. for 12 hours to obtain a paper feed roll of product 1 of the present invention. The hardness of this paper feed roll was 35 degrees. (2) Invention 2 Same as (1) above except that 50 parts of polytetramethylene glycol (PTMG 3000 manufactured by Sanyo Chemical Industries, Ltd.) with an average molecular weight of 3000 and a hydroxyl value of 34 to 40 was used as the reactive oligomer. Thus, a paper feed roll of Invention Product 2 was obtained. The hardness of this paper feed roll was 27 degrees. (3) Invention Product 3 4 parts of the same curing agent as in (1), liquid rubber with an average molecular weight of 2000 as a reactive oligomer (manufactured by Nippon Soda Co., Ltd.)
A paper feed roll of product 3 of the present invention was obtained in the same manner as in (1) except that 30 copies of NISSO PBG-2000) were used. The hardness of this paper feed roll was 25 degrees. (4) Comparative product A comparative product was prepared in the same manner as in (1), except that 5 parts of the curing agent and 30 parts of plasticizer (Benzoflex 9-88, manufactured by Versicol, molecular weight 341) were used. Got a paper roll. The hardness of this paper feed roll was 35 degrees. (5) Time-dependent changes in Nato resistance and friction coefficient of each paper feed roll Place each paper feed roll in a container, and then feed it with toner (Toner 1 or 2) or resin powder (polyester resin powder or AS resin powder). Cover the entire paper roll,
After being kept at 50℃ for 3 days and at room temperature for 200 days,
The powdered toner or resin adhered to the roll was removed, and the thickness of the toner or resin adhered to the roll was measured. The results are shown in Table 1. The numerical value indicates the thickness (mm) of the layer of toner or resin powder adhered to the surface of each roll. According to the paper feed roll of the present invention, at 50℃
Under both conditions of 1 day and 200 days at room temperature, there was no adhesion of toner or resin powder to the surface, and no bleeding occurred. On the other hand, in the comparative product, toner or resin powder adhered to a thickness of 0.5 to 1.0 mm. Next, each roll was left at room temperature for 200 days and -1

【table】

[Table] After being exposed to continuous temperature changes (heat cycle) of 6 hours at 0℃, 6 hours at room temperature, 6 hours at 60℃, and 6 hours at room temperature, each temperature was measured using a Heydon friction coefficient measuring device. The friction coefficient of the roll surface was measured. The results are shown in Table 2. According to the roll of the present invention, the friction coefficient did not change at all under any conditions, but the friction coefficient of the comparative product significantly decreased both at room temperature and under heat cycle conditions.

Claims (1)

[Claims] 1 having two or more hydroxyl groups in the molecule, based on 100 parts by weight of the urethane prepolymer obtained by reacting polyol and polyisocyanate, and
Reactive oligomers with an average molecular weight of 2000-3000
A method for producing a non-bleeding, low-hardness polyurethane molded article having a hardness of 10 to 60 degrees, comprising curing and molding a composition comprising 30 to 100 parts by weight and 2 to 8 parts by weight of a curing agent under heating.