JP2953097B2 - Method for producing polyurethane elastomer for cleaning blade with improved demolding time - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleaning brush used to scrape off toner remaining on a photosensitive drum surface of a copying machine or a laser beam printer.
The present invention relates to a method for producing a polyurethane elastomer for a card .

[0002]

2. Description of the Related Art Generally, a cleaning blade made of a polyurethane elastomer is prepared by using diphenylmethane diisocyanate (hereinafter referred to as MD) as a raw material for isocyanate.
I) Tolylene diisocyanate, naphthalene diisocyanate, dimethyl diphenylene diisocyanate and the like, and as a polyol material, a polyester diol such as ethylene adipate, butylene adipate and caprolactone, or a polyether diol such as polytetramethylene ether glycol, As a short-chain diol raw material, 1,4-butanediol (hereinafter, referred to as 1,
4-BG), trimethylolpropane (hereinafter T)
MP), or a mixture thereof, and reacting by a one-shot method or a prepolymer method to obtain a polyurethane elastomer and use it for a blade. Among them, workability, stability,
From the viewpoint of physical properties and the like, a method of forming a blade by an MDI prepolymer method is widely used.

[0003] In the prior art, since the time required for curing is long, as an improvement, the number of mold surfaces to be cast is increased, or an amine such as triethylenediamine or dimethylethanolamine is added to the curing agent side. The reaction has been accelerated by adding a system catalyst or a metal catalyst such as dibutyltin dilaurate or dioctyltin dilaurate, or by increasing the temperature of the prepolymer. However, it is not possible to increase the number of mold surfaces. If you want to speed up the reaction with a catalyst, etc. without shortening the productivity cycle,
Since the initial viscosity increase is accelerated, there are drawbacks such as poor casting, centrifugal molding, etc., which leave a crater-like pattern on the surface and cause blade failure. In addition, when the reactivity of the prepolymer is increased by increasing the temperature of the prepolymer, the stability of the prepolymer becomes inferior, and not only a blade having more stable physical properties cannot be obtained, but also poor casting due to an increase in viscosity. Therefore, workability was also inferior.

A blade used for cleaning a photosensitive drum of a copying machine, a laser beam printer, or the like is made of a thermosetting cast type polyurethane elastomer.
A liquid resin is poured in, and the mixture is further heated and reacted and cured to obtain a mold release / post blade from the mold. Alternatively, there is a method called centrifugal molding, in which a liquid resin is poured into the inside of a rotating drum to obtain a sheet having a uniform thickness by centrifugal force.

However, when a general MDI prepolymer is used and cured by reaction with 1,4-BG, TMP, or a mixture thereof, the demolding time from a mold or a drum is 40 to 50 minutes. And even if a catalyst or the like is added to these curing agents, it can be reduced to only about 30 minutes in relation to the pot life. If the resin is removed from the mold without waiting for the removal time, which is the possible removal time, the resin will be deformed and not only will not be able to obtain a blade with the correct size, There is a drawback such as causing the destruction of the material. If the blade does not have the correct size, a problem occurs in scraping off the toner, and the residual toner causes image contamination. This is a bottleneck, and in conventional polyurethane elastomers,
Improvements have been demanded without increasing productivity.

[0006]

SUMMARY OF THE INVENTION The present inventors have found that in the production of a cleaning blade using a thermosetting cast type polyurethane elastomer , the demolding time is short,
In order to suppress deformation of the molded product after molding,
As a result, a specific polyisocyanate and a specific number average molecular weight
Prepolymers derived from polyols
It has been found that improvement can be achieved by using an agent , and the present invention has been completed.

[0007]

That is, the present invention relates to a polyisocyanate comprising MDI and carbodiimide-modified MD.
I is used in a weight ratio within a range of 100/10 to 100/50, and the polyisocyanate and a number average molecular weight of 1,000 to 100 are used.
N obtained by reacting 3000 with a bifunctional polyol
CO content 5.0-8.0 wt% of the prepolymer, and hard
A diol having a number average molecular weight of 62 to 500,
Triol mixed polyol of 100/5 to 60/40
For cleaning blades characterized by reacting
This is a method for producing a polyurethane elastomer.

As the polyisocyanate for obtaining the prepolymer used in the present invention, the one in which the mixing ratio of MDI and carbodiimide-modified MDI is 100/10 to 100/50 by weight is used. The carbodiimide-modified MDI used in the present invention is produced, for example, by the method described in JP-B-45-7545 and JP-B-60-54951, and has an NCO content of 23 to 30%.

The bifunctional polyol having a number average molecular weight of 1,000 to 3,000 for obtaining the prepolymer used in the present invention includes:

Polyalkylene ether glycols such as poly (ethylene ether) glycol, poly (propylene ether) glycol and poly (tetramethylene ether) glycol (hereinafter abbreviated as PTG) and cyclic ethers such as ethylene oxide, propylene oxide, trimethylene oxide and Manufactured using tetrahydrofuran as an initiator with aliphatic diols such as ethylene glycol, 1,3-butanediol, 1,4-BG, diethylene glycol, dipropylene glycol, 1,2-propylene glycol and 1,3-propylene glycol. It is a polyether. Further, a mixture of the above-mentioned polyethers can also be used.

Polyester diols such as poly (ethylene adipate) diol, poly (propylene adipate) diol, poly (ethylene-propylene adipate) diol, poly (butylene adipate) diol,
Poly (hexamethylene adipate) diol and the like, and copolyester diols produced by polycondensation of ethylene glycol, propylene glycol and adipic acid, for example, poly (tetramethylene-ethylene adipate) diol, poly (1,4-butylene) -Propylene adipate) diol and poly (1,4-butylene-ethylene-propylene adipate) diol, but is not limited thereto. Examples of other polyester diols include caprolactone and / or dicarboxylic acids such as succinic acid, malonic acid, pimelic acid, sebacic acid and suberic acid, such as diols such as ethylene glycol, 1,2-propanediol, and 1,3.
-Also includes those produced by polycondensation with propanediol, 2,2-dimethyl-1,3-propanediol, 1,4-BG, 1,5-pentanediol, 1,6-hexanediol and the like. Also, mixtures of the above polyesters can be used.

When the number average molecular weight of the polyol is lower than 1,000, the hardness of the blade becomes too high,
Since the viscosity of the prepolymer becomes too high, it cannot be said to be preferable as a prepolymer for a blade.
On the other hand, if the number average molecular weight is more than 3,000, the hardness of the blade is too low or the rebound of the blade is too good, which is not a prepolymer suitable for the blade. Further, esters, lactones, PTG and the like cannot be said to be economically satisfactory raw materials if the number average molecular weight is out of this range because of the specialty of the polyol.

The method for producing a prepolymer used in the present invention comprises the steps of reacting a polyisocyanate with a polyol at a reaction temperature of 50.
It is a method of reacting at 100 ° C. for 1 to 5 hours.
The NCO content of this prepolymer is between 5.0 and 8.0% by weight.

In this case, if the NCO content of the prepolymer is lower than 5.0%, the viscosity of the prepolymer mainly increases, and if the NCO content is higher than 8.0%, the reactivity with the curing agent increases. Problems, such as too high speed and excessively high hardness of the resulting blade, make the blade unsuitable as a prepolymer for the blade.

In order to shorten the demolding time of the polyurethane elastomer, if a prepolymer is synthesized by using a trifunctional terminal OH polyol, the viscosity of the prepolymer is significantly increased, and the mixing and stirring with the crosslinking agent is difficult. Not only does it worsen, but the flowability to the mold also worsens, resulting in poor molding and is not a preferred method. In addition, when trifunctional or more triols such as TMP are introduced into the prepolymer, the viscosity of the prepolymer increases, the workability is deteriorated, and the time until demolding is shortened, but the pot life (visible time) becomes extremely short. Therefore, casting into a mold cannot be performed sufficiently, and this is not a preferable method.

The method for producing a polyurethane elastomer cleaning blade of the present invention, a prepolymer, hard
Diols having a number average molecular weight of 62 to 500
This is a method of reacting all with a mixed polyol .

A diol having a number average molecular weight of 62 to 500
For example, ethylene glycol, diethylene glycol
Propylene glycol, 1,4-BG, 1,3-butane
Tandiol, 1,6-hexanediol, neo pliers
Triglycol, hydrogenated bisphenol A, etc.
For example, glycerin, TMP, hexanetri
Oars and the like.

Preferably, 1,4-BG and TMP are fixed.
What is blended in a ratio is used favorably as a curing agent
You. The weight ratio of diol to short chain triol is 100 /
Used in the range of 5-60 / 40 .

When the amount of triol used is increased to obtain a cleaning blade, the time until demolding can be greatly shortened. However, if too much is used, general physical properties deteriorate, and particularly, tear strength and elongation are reduced. , The wear resistance most required as a blade is reduced. Or, in an extreme case, the hardness may be increased, and may even deviate significantly from the range of 60 ° (A) to 80 ° (A), which is the optimum hardness as a blade. Considering these points, it is preferable that the ratio of the short-chain triol such as TMP in the curing agent does not exceed 40% by weight. Also, the shorter demolding time means that
The curability is improved because the short-chain triol forms a cross-linking point and increases the cohesive force of the molecule. Therefore, if the number of crosslinking points in the resin is increased, the curability is improved, but it is not preferable to add more trifunctional components in the curing agent.

The prepolymer for a cleaning blade used in the present invention is characterized by problems of physical properties of the cleaning blade, problems of curability and demoldability at the time of molding of the cleaning blade, problems of viscosity of the prepolymer which affects workability,
Further, in order to satisfy economical efficiency such as productivity, MDI and carbodiimide-modified MDI are added to the polyisocyanate component.
It consists of Since the uretonimine group-containing MDI contained in the carbodiimide-modified MDI is trifunctional, a crosslinking point is eventually introduced. In addition, this introduction method can reduce the demolding time while maintaining the pot life to some extent without lowering the physical properties than the method of introducing a crosslinking point by using a large amount of TMP in order to accelerate the demolding property. The only way. Also, the method of the present invention,
It has advantages such as not significantly increasing the viscosity of the obtained prepolymer.

In the method for producing a polyurethane elastomer for a cleaning blade of the present invention, an antioxidant, a defoaming agent, an ultraviolet absorber, a reaction regulator and the like can be used as additives as required.

[0022]

The carbodiimide-modified MDI used in the present invention
The ureton imine group-containing MDI therein significantly accelerates the curability when cured with a predetermined curing agent, and can shorten the time until demolding. This is to speed up the development of physical properties of cross-linking points in the cured product and shorten the tack-free time. Also,
In the present invention, the amount of the carbodiimide-modified MDI used is not so large as to greatly increase the viscosity, so that the viscosity is in a range that can be easily handled as a prepolymer.

[0023]

EXAMPLES The present invention will be described by way of Examples and Comparative Examples.
Although described in more detail, the present invention is not limited by these. In Examples and Comparative Examples,
All "parts" mean "parts by weight" and all "%" mean "% by weight".

Examples 1 to 3 and Comparative Examples 1 to 4 Production of urethane prepolymer Various polyols having a number average molecular weight of 2,000 and two functional groups, MDI, carbodiimide-modified MD at the compounding ratio shown in Table 1
I was mixed and reacted at 75 ° C. for 3 hours to obtain a urethane prepolymer having an NCO content of 6.5%.

Preparation of polyurethane elastomer Measurement of viscosity, pot life and time to demolding of prepolymer. Viscosity of completed prepolymer, 1,4-BG
When a mixed polyol having a ratio of / TMP = 60/40 (weight ratio) was used as a curing agent, the pot life and the time until demolding were measured. The pot life is set at a prepolymer temperature of 80
℃, the temperature of the curing agent 30 ℃, these are NCO / OH
= 95/100 (molar ratio), and then sufficiently mixed and stirred for 30 seconds, and the increase in viscosity was observed in a 130 ° C oil bath. In addition, the demolding time was similarly measured by mixing and stirring, pouring the mixture into a centrifugal molding machine whose temperature had been adjusted to 130 ° C. in advance, and removing the mold. Table 1 shows the results.

[0026]

[Table 1]

Notes on Table 1 1) MDI is Millionate MT (manufactured by Nippon Polyurethane Industry). 2) Carbodiimide-modified MDI is Millionate MTL
(Manufactured by Nippon Polyurethane Industry), NCO content 29.0%,
The viscosity is 40 cP / 25 ° C. 3) Carbodiimide-modified MDI was Coronate 69 (manufactured by Nippon Polyurethane Industry), NCO content 26.9%, viscosity 1
00 cP / 25 ° C. 4) EA is ethylene adipate polyester polyol, number average molecular weight 2000, number of functional groups 2, acid value 56.1
mgKOH / g, acid value 0.5 mgKOH / g. 5) PCL is a polycaprolactone-based polyol, number average molecular weight 2000, number of functional groups 2, acid value 56.3 mg KOH
/ G, acid value 0.1 mgKOH / g.

[0028]

According to the present invention, the viscosity of the prepolymer used in the present invention is slightly increased as compared with the viscosity of the prepolymer not using liquid MDI, but compared with the prepolymer having a functional group introduced by another method. The viscosity is then at a low level. If the viscosity is about this example, poor mixing,
Problems such as poor casting and machine trouble can be easily avoided. In addition, since the pot life is at least 6 minutes, molding failure does not occur in both mold casting and centrifugal molding. Regarding the demolding time,
Examples 1 and 2 are 2/3 of Comparative Examples 1 and 2, which are conventional methods.
Could be shortened. Thus, in the production line of the cleaning blade, the molding cycle per blade can be shortened by using the same production equipment as before. Thereby, the productivity of the blade is improved, and the cost can be reduced.

Continuation of the front page (56) References JP-A-2-203372 (JP, A) JP-A-62-134678 (JP, A) JP-A-54-104840 (JP, A) JP-A-62-145274 (JP, A) JP-A-63-8865 (JP, A) JP-A-62-11719 (JP, A) JP-A-60-69681 (JP, A) JP-A-59-91473 (JP, A) 61-38968 (JP, A) Heikai 3-62377 (JP, U) Keiji Iwata, "Polyurethane Resin Handbook" (Showa 62-9-25), published by Nikkan Kogyo Shinbunsha p. 28, p. 75-76, p. 93 (58) Fields investigated (Int. Cl. ⁶ , DB name) C08G 18/00-18/87 C08L 75/00-75/16 G03G 21/00 CA (STN) REGISTRY (STN)

Claims (2)

(57) [Claims] 1. A polyisocyanate comprising diphenylmethane diisocyanate and carbodiimide-modified diphenylmethane diisocyanate in a weight ratio of 100/10 to 1: 1.
NCO content obtained by reacting the polyisocyanate with a bifunctional polyol having a number average molecular weight of 1,000 to 3,000 used in the range of 00/50 5.0 to 8.0% by weight
Each having a number average molecular weight of 6 as a prepolymer and a curing agent
2-500 diols and triols in 100 / 5-60
/ 40 mixed polyol is reacted
Made of polyurethane elastomer for cleaning blade
Construction method. 2. A number average molecular weight of 62 to 5 used for a curing agent.
00 is a 1,4-butanediol, and
Wherein the oar is trimethylolpropane.
The polyurethane for a cleaning blade according to claim 1.
A method for producing an elastomer.