JPH0397714A - Polyurethane elastomer - Google Patents

Abstract

PURPOSE:To obtain the title elastomer excellent in wear resistance and mechanical strength and little in the change of resilience with temperature by reaction between a polyisocyanate and a polyester diol with specified molecular weight made from a specific glycol mixture and alkanedicarboxylic acid. CONSTITUTION:Reaction is made at 80 deg.C for 2.5hr in a nitrogen atmosphere between (A) a polyester diol 1000-4000 in average molecular weight produced from a glycol mixture of (1) 90-50mol% of 1,6-hexanediol and (2) 10-50mol% of 1,2-propanediol and an alkanedicarboxylic acid of the formula (n is 2-8) (e.g. succinic acid) and (B) a polyisocyanate (e.g. 4,4'-diphenylmethane diisocyanate) into a free isocyanate group-contg. prepolymer, which is then reacted with a polyol at 130 deg.C and cured, thus obtaining the objective elastomer to be used for e.g. the cleaning blades for electrophotographic apparatuses.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polyurethane elastomer that not only has wear resistance and high strength, but also has a small rate of change in impact resilience with respect to temperature.

In general, members made of polyurethane elastomers used in electronic devices have excellent mechanical strength, abrasion resistance, hydrolysis resistance, and ozone resistance, and the temperature dependence of these properties is small. is required.

In particular, in electrostatic electrophotographic copying machines that use regular paper as recording paper, an electrostatic latent image is formed by applying an electrostatic charge to the surface of the photoreceptor by discharging it and then exposing the image thereon. Next, toner with opposite polarity is attached to the electrostatic latent image and developed, and the toner image is transferred to recording paper.Finally, the recording paper with the toner image transferred is heated and the toner is recorded. Copying is done by fixing on paper. Therefore, in order to sequentially copy onto multiple sheets of recording paper, in the above steps,
After the toner image is transferred from the photoreceptor to the recording paper, it is necessary to remove the toner remaining on the surface of the photoreceptor. One way to remove it is to press a blade against the surface of the photoreceptor and slide the photoreceptor. A blade cleaning method in which cleaning is performed by rubbing is known. A molded product made of polyurethane elastomer is preferably used as a blade for this blade cleaning method because it has particularly excellent mechanical strength such as abrasion resistance.

Conventionally, such polyurethane elastomers are generally made of commercially available polyols, such as polyester polyols such as polyethylene adipate ester polyol, polyethylene butylene adipate ester polyol, cabrolactone ester polyol, and polyoxypropylene glycol. It is produced by the reaction of an ether polyol with a polyisocyanate such as 4,4'-diphenylmethane diisocyanate.

However, such conventional cleaning blades made of polyurethane elastomer have a large rate of change in impact resilience with respect to temperature. Therefore, in order to improve impact resilience at low temperatures, for example, the polyisocyanate content may be increased. A method using a difunctional low molecular weight cross-linking agent has also been proposed, but this method results in significantly higher impact resilience at high temperatures, causing the blade to easily sag. . On the other hand, in order to reduce the rebound resilience at high temperatures,
A method using a large amount of a trifunctional or higher polyfunctional crosslinking agent has also been proposed. According to this method, the rebound resilience at high temperatures can be reduced to some extent, but the glass transition point of the resulting elastomer increases significantly and the elastomer becomes glassy at low temperatures, making cleaning at low temperatures difficult. The characteristics deteriorate significantly.

As described above, there has been no known cleaning blade that has appropriate repulsion resiliency from a low temperature range to a high temperature range. The use of polycarbonate polyols has also been proposed in order to reduce impact resilience at high temperatures, but this significantly increases the glass transition point of the resulting elastomer.

Therefore, in order to solve this problem in cleaning blades, for example, Japanese Patent Application Laid-Open No. 59-91473 discloses an average molecule consisting of a mixed glycol of 1,6-hexanediol and neobentyl glycol and adipic acid. A cleaning blade for an electrophotographic machine has been proposed in which the hydrolysis resistance is particularly improved by reaction-curing a polyester diol of iiiooo to 4000 and a polyisocyanate. Similarly, JP-A-6069
681, 1,6-hexanediol and 1.4
- It has been proposed to use mixed glycols with butanediol.

Furthermore, Japanese Patent Application Laid-Open No. 63-8685 typically includes:
Alkanedicarboxylic acid such as adipic acid and carbon number 4~
10 alkanediol, that is, a polyester diol obtained by reacting with a glycol such as butylene glycol or hexane diol, is reacted and cured with polyisocyanate to reduce the temperature dependence of rebound resilience. It is proposed to get a blade.

As mentioned above, various polyurethane elastomers have already been proposed with the aim of improving hydrolysis resistance and the temperature dependence of impact resilience. cannot be said to have been sufficiently improved.

Therefore, as a result of intensive research in order to solve the problems with conventional polyurethane elastomers as described above, especially cleaning blades for electrophotographic copying machines, the present inventors found that 1, An average molecule fi consisting of a glycol mixture consisting of 6-hexanediol and 1,2-propanediol and an alkanedicarboxylic acid represented by adipic acid.
Hardness (J
IS A) is in the range of 65 to 80, and 0 to 60
The present invention was achieved by discovering that it is possible to obtain a polyurethane elastomer in which the temperature dependence of rebound resilience is extremely small in the temperature range of .degree.

The polyurethane elastomers according to the invention for making bows are (all,
A glycol mixture consisting of 90 to 50 mol% of 6-hexanediol and 10 to 50 mol% of 1,2-brobanediol, and (bl general formula HOOC- (CH2) n-COOH (where n is 2
The number is 8. ) It is characterized by being formed by reaction-curing a polyester diol having an average molecular weight i of 11,000 to 4,000 and consisting of an alkanedicarboxylic acid represented by the following formula and a polyisocyanate.

The glycol mixture used in the present invention consists of 90-50 mol% of 1,6-hexanediol and 10-50 mol% of 1,2-propanediol.

Generally, the impact resilience of polyurethane elastomers is related to the ease of micro-Brownian motion of the soft segment chains, and the reason why the impact resilience increases in the high temperature range of 40 to 60"C is due to the micro-Brownian motion of the soft segment chains. In addition, secondary bonds such as hydrogen bonds between hard segment chains and soft segment chains and weak hydrogen bonds between soft segment chains are cleaved, increasing the mobility of the soft segment 111. Therefore, in the present invention, in order to suppress the mobility of the soft segment chains as described above, by using the polyol component as described above, it is possible to introduce an appropriate amount of side chain methyl groups into the molecule. It is possible to increase internal viscosity and reduce impact resilience in a high temperature range of 40 to 60°C.

On the other hand, in general, polyurethane elastomers have low impact resilience in the low temperature range of 0 to 20° C. as a result of their molecular movement being suppressed. However, by using a certain polyol as described above, the phase separation structure inside the polyurethane changes due to the presence of side chain methyl groups, increasing molecular mobility, and as a result, impact resilience is increased.

Therefore, according to the present invention, when a predetermined glycol mixture as described above is used as a polyol component, a polyurethane elastomer whose impact resilience is particularly low in temperature dependence can be obtained.

Next, the alkanedicarboxylic acid used in the present invention is
It is represented by the general formula HOOC-(CH2)n--Coo}I (wherein, n is a number from 2 to 8). In the above general 2, when n is smaller than 2 or when n is larger than 8, a polyurethane elastomer having the desired excellent physical properties cannot be obtained.

Therefore, suitable alkanedicarboxylic acids for use in the present invention include succinic acid, glutaric acid, acyhinic acid,
Examples include pimelic acid, suberic acid, azelaic acid, and sebacic acid, but succinic acid, glutaric acid, and adipic acid are particularly preferred from a practical standpoint.

The polyester diol used in the present invention can be obtained by condensing the above-mentioned glycol mixture and the above-mentioned alkanedicarboxylic acid according to a conventional method.

The polyisocyanate used in the present invention is not particularly limited, and those used in the production of polyurethane elastomers are generally used. For example, tolylene diisocyanate, 4.4'-diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate, 1,5 naphthalene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, polymethylene polyphenyl polyisocyanate, p-
Examples include phenylene diisocyanate and cyclohexane diisocyanate.

According to the present invention, the polyester diol and polyisocyanate are reacted according to a conventional method to obtain a urethane polymer, and then a curing agent is added thereto and the polymer is reacted and cured. More specifically, usually 70 to 120°C, 5fl
The polyester diol and the polyisocyanate are each dehydrated under reduced pressure below Hg for 2 to 4 hours, mixed, and then dried at a temperature of 50 to 120°C under an inert atmosphere for 1 to 5 hours.
A prebolimer is obtained by reacting for a period of time.

Next, a curing agent is added to this brevolimer so that the isocyanate index defined by the number of moles of isocyanate groups/the number of moles of hydroxyl groups is in the range of 1.00 to 1.20, and the resulting liquid mixture is Secondary crosslinking is carried out at 160°C, followed by ripening at room temperature to obtain a polyurethane elastomer.

For example, to manufacture a cleaning blade for an electrophotographic machine, the liquid mixture thus obtained is formed into a plate shape by a conventional method, for example, by centrifugal casting or by casting into a desired mold. After being shaped, heat treated and matured,
It is cut according to the specifications of the electrophotographic copying machine used.

Examples of the curing agent include ethylene glycol, diethylene glycol, brobylene glycol, 1,4-
Butanediol, 2,3-butanediol, 1.3-butanediol, 1.5-pentanediol, 1.6-hexanediol, Ll,1-trimethylolbroban,
Glycerin, pentaerythritol, hydroquinone bis(β-hydroxyethyl) ether, etc. are used.

As described above, according to the present invention, a mixture containing 1,6-hexanediol and propylene glycol in a predetermined ratio is used as the polyol component, and an appropriate amount of methyl group is added to the polyol component. Therefore, it is possible to obtain a polyurethane elastomer whose rebound resilience has small temperature dependence over a wide temperature range of 0 to 60°C.

In particular, according to the present invention, it is possible to obtain a polyurethane elastomer having a rebound resilience at 0° C. of 20 or more and a rebound resilience at 60° C. of 70 or less.

Therefore, a cleaning blade for an electrophotographic machine made of such a polyurethane elastomer has excellent cleaning performance even at low temperatures.

EXAMPLES The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples in any way.

Example 1 Using a mixed glycol consisting of 90 mol% of 1,6-hexanediol and 10 mol% of 1,2-propanediol and adipic acid, an average molecular weight of 2029 was prepared according to a conventional method.
, a polyester diol having a hydroxyl value of 55.3 was prepared.

100 parts by weight of this polyester diol and 48.0 parts by weight of 4,4゛diphenylmethane diisocyanate were reacted for 2.5 hours at 80°C in a nitrogen atmosphere to obtain a brepolymer with a free isocyanate content of 8.1%. Ta.

Next, 8.5 parts by weight of a mixture of 1,4-butanediol/trimethylolpropane (equivalent ratio: 82/12) was added to 100 parts by weight of this Brevolimer, and 2 parts by weight were added at 130°C.
The reaction was carried out for a period of time to obtain a polyurethane elastomer having a JIS A hardness of 76°.

Regarding this polyurethane elastomer, JISK 6
According to the method described in No. 301, impact resilience was measured over a range of 0 to 60°C. The results are shown in Table 1.

Example 2 Using a mixed glycol consisting of 70 mol% of 1,6-hexanediol and 30 mol% of 1,2-propanediol and adipic acid, the average molecular weight ffi2 was determined according to a conventional method.
0.070 and a hydroxyl value of 54.2.

100 parts by weight of this polyester diol and 4 parts of 4,4'diphenylmethane diisocyanate 7. 1 part by weight was reacted at 80° C. for 3 hours in a nitrogen atmosphere to obtain a prebolimer with a free isocyanate content of 7.9%.

Next, 8.3 parts by weight of a mixture of 1.4-butanediol/trimethylolpropane (equivalent ratio: 82/12) was added to 100 parts by weight of this Brevolimer, and the mixture was reacted at 140°C for 2 hours to obtain a JIS A hardness of 77. A polyurethane elastomer of .degree. was obtained.

Regarding this polyurekne elastomer, JTSK 6
According to the method described in No. 301, impact resilience was measured over a range of 0 to 60°C. The results are shown in Table 1.

Example 3 Using a mixed glycol consisting of 50 mol% of 1,6-hexanediol and 50 mol% of 1,2-brobanediol and adipic acid, an average molecular weight of 1972 was prepared according to a conventional method.
, a polyester diol having a hydroxyl value of 56.9 was prepared.

100 parts by weight of this polyester diol and 4 parts by weight of 4,4'-diphenylmethane diisocyanate 8. The mixture was reacted with 1 part by weight at 70° C. under a nitrogen atmosphere for 3 hours to obtain a Brevolimer with a free isocyanate content of 7.8%.

Next, 8.2 parts by weight of a mixture of 1.4=butanediol/trimethylolbroban (equivalent ratio 82/18) was added to 100 parts by weight of this prebolymer, and 1.4 parts by weight was added at 140°C.
The reaction was carried out for a period of time to obtain a polyurethane elastomer having a JIS A hardness of 77°.

Regarding this polyurethane elastomer, JISK 6
The impact resilience was measured over the range of 0 to 60° C. according to the method described in No. 301. The results are shown in Table 1.

Example 4 Using a mixed glycol consisting of 70 mol% of L6-hexanediol and 30 mol% of 1,2-propanediol and succinic acid, a polyester diol with an average molecular weight of 1993 and a hydroxyl value of 56.3 was produced according to a conventional method. Prepared.

Using this polyester diol, a bre polymer was obtained in almost the same manner as in Example 1 under the conditions shown in Table 1.
Next, a curing agent was added and reacted to obtain a polyurethane elastomer. The first is impact resilience in the range of 0 to 60℃.
Shown in the table.

Example 5 Using a mixed glycol consisting of 70 mol% of 1,6-hexanediol and 30 mol% of 1,2-propanediol and glutaric acid, according to a conventional method, the average molecule it20
5, a polyester diol having a hydroxyl value of 54.6 was prepared.

Using this polyester diol, a bre polymer was obtained in almost the same manner as in Example 1 under the conditions shown in Table 1.
Next, a curing agent was added and reacted to obtain a polyurethane elastomer. The first is impact resilience in the range of 0 to 60℃.
Shown in the table.

Comparative Example 1 Using 1,6-hexanediol and adipic acid, an average molecular ffi of 2051 and a hydroxyl value of 54.
A polyester diol of No. 7 was prepared.

Using this polyester diol, a prepolymer was obtained in substantially the same manner as in Example 1 under the conditions shown in Table 1.
Next, a curing agent was added and reacted to obtain a polyurethane elastomer. The first is impact resilience in the range of 0 to 60℃.
Shown in the table.

Comparative Examples 2 to 12 Using glycol components and dicarboxylic acids shown in Table 1, polyester diols were prepared according to conventional methods, and using these polyester diols, the example process was carried out under the conditions shown in Table 1. A prebolimer was obtained in substantially the same manner as above, and then a curing agent was added and reacted to obtain a polyurethane elastomer. Table 1 shows the impact resilience in the range of 0 to 60°C.

The polyurethane elastomer according to the present invention has a rebound resilience of 20 or more at 0° C. and a rebound resilience of 70 or less at 60° C., and the temperature dependence of the rebound resilience is small.

On the other hand, the polyurethane elastomer according to the comparative example has an impact resilience at O'c of over 20 or an impact resilience at 60°C of over 70,
This shows that the rebound resilience has a large temperature dependence.

Further, Table 1 shows the results of processing the polyurethane elastomers obtained in Examples and Comparative Examples into predetermined dimensions, producing cleaning blades, and performing continuous copying at 0°C and 60°C.

The cleaning blade of the present invention has excellent cleaning properties in the range from low temperature (0° C.) to high temperature (60° C.), and is shown to be free from poor cleaning and no squealing.

Claims (4)

[Claims] (1) (a) A glycol mixture consisting of 90 to 50 mol% of 1,6-hexanediol and 10 to 50 mol% of 1,2-propanediol, and (b) General formula HOOC-(CH_2)_n-COOH ( In the formula, n is a number from 2 to 8.) A polyurethane elastomer obtained by reaction-curing a polyester diol having an average molecular weight of 1,000 to 4,000 and consisting of an alkanedicarboxylic acid represented by the following formula and a polyisocyanate. (2) The polyurethane elastomer according to claim 1, wherein the alkanedicarboxylic acid is succinic acid, glutaric acid, or adipic acid. (3) (a) A glycol mixture consisting of 90 to 50 mol% of 1,6-hexanediol and 10 to 50 mol% of 1,2-propanediol, and (b) General formula HOOC-(CH_2)_n-COOH ( In the formula, n is a number from 2 to 8. blade. (4) The cleaning blade for an electrophotographic machine according to claim 3, wherein the alkanedicarboxylic acid is succinic acid, glutaric acid, or adipic acid.