JPH09176268A - Flame-retardant urethane foam and conductive roll - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive roll which exhibits no variation in electrical resistance, does not stain a photoreceptor, is excellent in environment dependence and stability under continuously applied voltage, has a good moldability, and is inexpensive. SOLUTION: A conductive roll is produced from a urethane foam formed by reacting a polyisocyanate with a polyol which is produced by the addition reaction between a polyfunctional polyether glycol and 20-50wt.% polycaprolctone and has an average mol.wt. of 3,000-5,000 and a mol.wt. distribution of 1.0-1.2. The foam contains a brominated arom. triazine compd. as a flame retardant and a symmetrical quaternary ammonium salt as a conductive filler.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flame-retardant urethane foam having good low-temperature characteristics, and particularly to a bias such as a charging roll, a transfer roll, a cleaning roll or the like incorporated in an electrophotographic device such as a copying machine, a printer or a facsimile. It is most suitable for use as a conductive roll used by applying a voltage.

[0002]

2. Description of the Related Art Conventionally, urethane foams have been used as cushioning agents for seats of automobiles, trains, etc., and various buffer agents, but these urethane foams are required to have flame retardancy. Further, as a general characteristic of these, the hardness increases in a low temperature environment. Therefore, there is a demand for urethane foam having excellent low temperature characteristics.

On the other hand, since each roll for charging, transferring, and cleaning used in an electrophotographic apparatus is required to have proper elasticity and hardness and proper and uniform conductivity, it has been generally used in the past. Urethane rubber, silicone rubber, chloroprene rubber, etc. are used. Among them, urethane rubber is particularly preferable from the viewpoints of excellent wear resistance and compression set resistance and non-contamination on the surface of the photoconductor. Is used. Further, such a conductive roll is also required to have flame retardancy.

[0004]

As the polyurethane rubber used for the flame-retardant member typified by the conductive roll as described above, various polyether polyols or polyester polyols are usually used alone.

Here, a wide range of products, from soft to hard, can be obtained from polyether polyols, and tensile strength, abrasion resistance, heat aging resistance, ozone resistance, chemical resistance, cold resistance,
It has excellent rubber elasticity and electrical properties, but has the disadvantage of poor mechanical strength.

On the other hand, polyester polyol has excellent mechanical strength and a product having a wide range of physical properties can be obtained, but it has the drawbacks of poor cold resistance and electrical characteristics. Polycaprolactone polyols, in particular, have a relatively low viscosity and are excellent in heat resistance, hydrolysis resistance, and low-temperature characteristics of polyurethane polymers, but have the drawback that they tend to cause crystallization.

Further, in order to reduce the hardness, it is possible to use a material having a large molecular weight and to extend the distance between the crosslinking points, but this may raise the viscosity and hinder the molding. Further, those having a large molecular weight distribution have problems that the reaction is non-uniform and contamination of the photoconductor is likely to occur.

Further, in general, in order to impart flame retardancy,
A flame retarding agent is added. However, when an organic phosphoric acid ester or the like, which is an additive type flame retardant that has been used conventionally, is used, it is possible to impart self-extinguishing property to the polyurethane layer, and thus the flame retardant effect is excellent, but this compound is used on the roll surface. There is a problem of bleeding, especially when used as a conductive roll, there is a problem of easily contaminating the photoconductor. On the other hand, those to which a phosphorus-containing polyol or the like which is a reactive flame retardant has been added do not contaminate the organic photoconductor or the like even when used as a conductive roll, but the phosphorus-containing polyol has a molecular weight of There is a problem that it is difficult to secure sufficient conductivity because the ions are small and difficult to move.

Generally, a conductivity-imparting agent is added to impart conductivity. However, in the type in which conductive fine particles such as conductive carbon black are mixed, there is no proportional relationship between the added amount of conductive fine particles and the resistance, and it is difficult to control the resistance value by the added amount. ， There is a problem that the quality varies from lot to lot. Further, in order to obtain a desired resistance value, it is necessary to add a large amount of conductive fine particles, and as a result, there is a problem that the hardness of rubber is increased. On the other hand, when an ionic conductive agent such as an alkali metal salt is used, a desired resistance value can be easily obtained by establishing a proportional relationship between the added alkali metal salt and the resistance value. . However, since the mobility of ions strongly depends on the water absorption of the rubber material and the temperature, the resistance value greatly varies depending on the temperature and humidity of the environment in which it is used. Further, there is a drawback that the initial quality cannot be maintained because the resistance value increases due to continuous application of voltage.

As described above, there has been a demand for the appearance of a flame-retardant polyurethane having a good low-temperature characteristic, there is no variation in the electrical resistance, there is no stain on the photoreceptor, and there is no environmental dependency of the roll or continuous. It has been desired to develop a conductive roll that has excellent application stability, good moldability, and is inexpensive.

[0011]

A first aspect of the present invention for solving the above-mentioned problems is to add polycaprolactone (PCL) in an amount of 20% to 50% to a polyfunctional polyether glycol and have an average molecular weight of 3000. .About.5000, a urethane foam using a reaction product of a polyisocyanate and a polyol having a molecular weight distribution of 1.0 to 1.2, and containing a brominated aromatic triazine compound as a flame retardant imparting agent. A flame-retardant polyurethane foam characterized by.

Here, the content of the brominated aromatic triazine compound is, for example, 5 to 50 parts by weight based on 100 parts by weight of the polyol.

The second aspect of the present invention is to add polycaprolactone (PCL) to polyfunctional polyether glycol in an amount of 20%.
% -50%, average molecular weight of 3000-50
00, a polyol having a molecular weight distribution of 1.0 to 1.2, and a urethane foam using a reaction product of a polyisocyanate as a material, containing a brominated aromatic triazine compound as a flame retardant imparting agent, and being electrically conductive. A conductive roll containing a symmetrical quaternary ammonium salt as a property imparting agent.

Here, the content of the brominated aromatic triazine compound is, for example, 5 to 50 parts by weight with respect to 100 parts by weight of the polyol.

The content of the symmetrical quaternary ammonium salt is, for example, 0.05 to 20 parts by weight with respect to 100 parts by weight of the polyol.

The conductive roll of the present invention further comprises:
It is preferable to contain conductive carbon black as the conductivity-imparting agent.

The content of the conductive carbon black is, for example, 100 parts by weight of the polyol.
It is 0.5 to 5.0 parts by weight.

The flame-retardant polyurethane foam of the present invention comprises
In order to satisfy the required proper elasticity, hardness, low temperature characteristics, and uniform conductivity, the basic skeleton of the polyol main chain has tensile strength, wear resistance, and
Polyether polyol with excellent heat aging resistance, ozone resistance, chemical resistance, cold resistance, rubber elasticity, and electrical characteristics
A polyester polyol modified with polycaprolactone having excellent mechanical strength is used for the terminal.
In the present invention, by adding 20 to 50% of polycaprolactone, a polyether ester copolymer polyol having a glass transition temperature (Tg) of −70 ° C. or lower and an amorphous main chain portion is obtained.

As described above, the polyether ester copolymer polyol used in the present invention is a rubber-like elastic body having a Tg of -70 ° C. or less, is stable against temperature and humidity, and has a resistance value fluctuation even at low temperatures. small. Therefore, in particular, the conductive urethane elastic body using the same can fulfill the function of forming a high quality image.

In the present invention, in order to realize this, an amorphous polyether polyol such as PPG (polyoxypropylene glycol) is used as the basic skeleton of the polyol. This amorphous property is due to the irregularity caused by the asymmetric irregular arrangement of the polymer chain shown in the following formula (I) and the conformation shown in the following formula (II).

[0021]

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[0022]

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Further, the polyether ester copolymer polyol used in the present invention has a large dipole moment in the ether oxygen of the main chain, so that a large amount of salt can be dissolved,
The salt can be easily moved by coupling with the movement of the molecular chain. In addition, the polyurethane foam of the present invention has an advantage that various manufacturing conditions are not strict as compared with polyester urethane foam.

On the other hand, the introduction of lactone, which is an ester, at the terminal has the advantages that mechanical strength can be increased and cell uniformity can be added.

As described above, a wide range of products from soft to hard can be obtained in the main chain skeleton, and tensile strength, wear resistance, heat aging resistance, ozone resistance, chemical resistance, cold resistance, rubber elasticity, Polyether polyol, which has excellent electrical properties but poor mechanical strength, is introduced, and at the end, products with excellent mechanical strength and a wide range of physical properties can be obtained, but polyester polyols with poor cold resistance and electrical properties are used. By introducing them, the drawbacks of each other can be compensated. In particular, polycaprolactone polyol has a relatively low viscosity and is excellent in heat resistance, hydrolysis resistance and low temperature characteristics of polyurethane polymer. For this reason, the polycaprolactone addition rate in the present invention is
20% to 50% is preferable.

Further, in the present invention, the use of a polyfunctional polyol, particularly a trifunctional polyol, suppresses an increase in the viscosity, and further, in order to reduce the hardness without hindering the molding, the average molecular weight is Is 3000 to 5000, especially 37
It is set to 50 to 4250. Regarding the molecular weight distribution, a large distribution tends to cause nonuniform reaction and contamination of the photoconductor, so 1.0 to 1.2 is preferable.

In the flame-retardant polyurethane foam of the present invention, addition-type flame retardants such as halogen-based and inorganic flame-retardants can be used as the flame-retardant imparting agent, but especially decabromo. It is preferable to use a brominated aromatic triazine compound which is a diphenyl oxide substitute compound.
This is because other than this, good flame retardancy cannot be exhibited. The content of the brominated aromatic triazine compound is 5.0 to 5 with respect to 100 parts by weight of the polyol.
0.0 parts by weight, preferably 10.0 to 30.0 parts by weight. This is because if it is less than this range, it becomes difficult to exhibit good flame retardancy, and if it is more than this range, it becomes difficult to uniformly disperse and maintain the cell structure.

In the flame retarding mechanism of the present invention, first, the chemical reaction is stopped at the stage of combustion, and the gas impedes contact with oxygen and slows the transfer of heat. Next, bromination → debromination →
The double bond is repeated to form a polymer residue containing a large amount of carbon.

Specifically, it has the effect of lowering the concentration of active OH radicals and H radicals in the following reactions that occur during the burning of polymers.

HO ^· + CO → CO ₂ + H ^· (A) Exothermic H ^· + O ₂ → HO ^· + O ^· (B) For example, in this case, the generated hydrogen bromide is converted into highly reactive OH radicals (HO ^· ). react.

[0031] ^{HO · + HBr → HOH + Br} · (C) inhibited the reaction ^{Br · + RH → HBr + R} · (D) regeneration reaction where, RH is a polymer containing hydrogen, highly reactive instead of OH radicals (HO ^·) Br radical (B
chain reaction is stopped r ^·) or can R radical (R ^·). Further, the Br radical halogenates the polymer molecule, then causes dehydrohalogenation, forms a double bond, and promotes carbonization.

Due to the flame retardant mechanism described above, the polyurethane foam of the present invention exhibits good flame retardancy, and can be suitably used for various sheet materials, cushioning agents and the like.

The urethane foam of the present invention is particularly suitable for use as a conductive roll. That is, by adding a conductivity imparting agent, good and uniform electric characteristics can be obtained.

Here, it is preferable to use a symmetrical quaternary ammonium salt as the conductivity-imparting agent. this is,
By using the symmetrical quaternary ammonium salt, it is possible to reduce the fluctuation of the resistance value due to the temperature and humidity of the environment and the change with time of the resistance value due to continuous voltage application. That is, when the symmetric quaternary ammonium salt is used, the mobility and diffusivity of the conductive agent are appropriately reduced even if the temperature and humidity of the environment change, and the resistivity becomes relatively constant. can do. As a result, a constant current of the resistivity of the conductive polyurethane elastic body and a significantly lower charging rate are generally achieved, and the extension of the electrical life can be provided. The reason for the symmetry is that the asymmetry has a drawback that the mobility and diffusibility are excessively reduced and the number of added parts is increased.

The symmetrical quaternary ammonium salt as the conductivity-imparting agent is preferably an alkyl group having 2 or more carbon atoms or a derivative having this as a basic skeleton, and the counter anion is halogen ion, sulfate ion, sulfone. Acid ions and fluoro ions are preferred. Also, a small amount of conductive carbon black can be further added as a kind of doping.

In the present invention, the content of the symmetrical quaternary ammonium salt is 0.05 based on 100 parts by weight of the polyol.
˜20.0 parts by weight, preferably 0.1 to 10.0 parts by weight. This is because if it is less than this range, good conductivity cannot be obtained, and if it is more than this range, it is difficult to disperse uniformly and the cost is increased.

Furthermore, by adding a small amount of carbon black, it is possible to further reduce the change with time in resistance value due to continuous voltage application. Carbon black acts as an intermediate medium for charge transfer by ions.
By dispersing carbon black in the material matrix, the migration distance of the charge-carrying ions is gradually reduced, the effect of environmental changes on the ion mobility is gradually reduced, and the rate of polarization of the ions is suppressed, resulting in resistance. Increases environmental stability over time. In other words, it is doping into the ionic electrolyte. The amount of conductive carbon black is usually 0.5 to 5 with respect to 100 parts by weight of polyol.
0 parts by weight is preferable, and 1.0 to 3.0 parts by weight is particularly preferable. This is such an amount that carbon black alone does not exhibit a desired resistance value of the roll, that is, does not form a so-called developed carbon structure. When the amount of the conductive carbon black added exceeds the above range, the obtained electric resistance value varies greatly, and not only a copy having good image quality cannot be obtained, but also the viscosity of the polyurethane-forming raw material increases too much. Moldability also tends to deteriorate, and both are not preferable.

The polyurethane foam of the present invention is prepared by mixing the above-mentioned polyol with polyisocyanate, a flame retardant-imparting agent, a conductivity-imparting agent and various other additives, a foam stabilizer, a catalyst and the like in a conventional manner. It can be molded into a desired shape by molding and thermosetting.

As the polyisocyanate, conventionally known ones may be used, for example, 2,6-toluene diisocyanate (TDI), 4,4′-diphenylmethane diisocyanate (MDI), paraphenylene diisocyanate (PPDI), 1, 5-naphthalene diisocyanate (NDI), 3,3-dimethyldiphenyl-
4,4'-diisocyanate (TODI) and the like can be mentioned.

The mixing ratio of the polyol and the polyisocyanate may be a general one, and for example, the active hydrogen such as the hydroxyl group of the polyol and the isocyanate group are mixed so as to be approximately equimolar.

The catalyst, foam stabilizer and the like may be the same as those used in the prior art. For example, as a catalyst, triethanolamine (TEA), 1,4-diaza [2,2,
2] Bicyclooctane (DABCO), diazabicycloundecene (DBU), and the like, and examples of the foam stabilizer include organic modified silicone oil and the like.

[0042]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to examples and comparative examples.

(Examples 1 to 6) Polypropylene glycol (PPG) having a molecular weight shown in Table 1 below was added so that the proportion after addition of polycaprolactone would be the weight shown below. A polyol having a molecular weight distribution and a glass transition temperature was produced.

Using these 6 kinds of polyols, to 100 parts by weight of each of these polyols, 2.0 parts by weight of a silicone type foam stabilizer, 0.04 parts by weight of an amine type catalyst, and a crude ( Crude) MDI was blended so that the index (NCO / OH) would be 1.10, mixed and cast, and thermoset at 110 ° C. for 30 minutes to mold each urethane foam.

Table 1 also shows the results of testing the uniformity of the cells, the stain resistance of the photoreceptor and the physical properties of the polyurethane foam thus produced.

(Comparative Examples 1 to 4) For comparison, polycaprolactone was similarly added to polyoxypropylene glycol having various molecular weights to obtain the polyols shown in the table below. The foam was molded. Table 1 also shows the results of the similar tests of cell uniformity, photoreceptor stain resistance, and physical properties of these polyurethane foams.

[0047]

[Table 1]

As is clear from the results shown in Table 1, the polyurethane foam using the polyol falling within the range of the present invention had good cell uniformity, photoreceptor contamination and physical properties, but after addition of polycaprolactone. The comparative example 1 having a small molecular weight and the comparative example 2 having a large polycaprolactone addition ratio were not preferable in all. Further, it was revealed that when a polyol having a molecular weight distribution outside the range of the present invention was used (Comparative Examples 3 and 4), the stain resistance of the photoconductor was not good.

(Flame Retardancy Test) Using the polyol used in Example 4, 15.0 parts by weight of a flame retardant-providing agent shown in Table 2 below was added to 100 parts by weight of this polyol to prepare a polyurethane. A foam was produced. When a flame retardancy test was conducted on each polyurethane foam based on UL94, it became clear that when a brominated aromatic triazine compound was used as a flame retardant imparting agent, it satisfied the HBF standard. It was

For comparison, Mg was used as a flame retardant-imparting agent.
When (OH) ₂ was used and Al (OH) ₃ was used, good flame retardancy was not obtained.

Further, as the polyol, polypropylene glycol (PPG) or polycaprolactone (P
CL) was used alone to similarly mold a polyurethane foam to which various flame retardant-imparting agents were added, and a flame retardancy test was conducted in the same manner, but good flame retardancy was not obtained in any case. It was

The results are shown in Table 2.

[0053]

[Table 2]

(Conductivity Test 1) Using the polyol of Example 4 above, 100 parts by weight of this polyol was added to a symmetrical quaternary ammonium salt (tetraethylammonium paratoluenesulfonate: (Et) ₄ N ⁺ p-). 0.5 parts by weight of TsO ⁻ ) is added to mold a polyurethane foam,
The change in conductivity over time was measured. For comparison, the change in conductivity with time was similarly measured using an alkali metal salt of lithium perchlorate (LiClO ₄ ) as a conductivity-imparting agent. The conductivity was measured by applying a load of 500 g × 2, and measuring the resistance when +500 V was applied in an environment of a temperature of 23 ° C. and a humidity of 55%.

The results are shown in FIG. As a result, it has been clarified that the use of a symmetric quaternary ammonium salt as the conductivity-providing agent exhibits better stability of conductivity.

(Conductivity Test 2) Using the polyol of Example 4 above, the same as in Conductivity Test 1 (Et) ₄ N ⁺ p-Ts.
O ^- with the addition of further carbon black E
A polyurethane foam doped with 1 part by weight of C-P was produced, and the changes in conductivity of both of them with time and the environmental dependence were measured. The results are shown in FIGS. 2 and 3. In addition,
The measurement conditions for conductivity are the same as those for conductivity test 1, but the measurement environment is LL (10 ° C, 30%), NN (23 ° C, 55%).
%) And HH (35 ° C., 80%).

As a result, it was found that the one using carbon black together with (Et) ₄ N ⁺ p-TsO ⁻ exhibits more stable conductivity.

[0058]

According to the present invention, a novel flame-retardant urethane foam excellent in low-temperature characteristics can be obtained. Especially, when it is used for a conductive roll, there is no variation in electric resistance value, and there is no environmental dependence of the roll. It is possible to obtain a roll which has improved stability of continuous application, good moldability, low cost, and excellent safety.

[Brief description of the drawings]

FIG. 1 is a diagram showing a result of a flame retardancy test.

FIG. 2 is a diagram showing a result of a conductivity test 1.

FIG. 3 is a diagram showing a result of a conductivity test 2.

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Claims (7)

[Claims] 1. A polyol having an average molecular weight of 3000 to 5000 and a molecular weight distribution of 1.0 to 1.2, which is obtained by adding 20% to 50% of polycaprolactone (PCL) to a polyfunctional polyether glycol, and a polypolyether. A flame-retardant polyurethane foam comprising a urethane foam using a reaction product with an isocyanate as a material, and containing a brominated aromatic triazine compound as a flame-retardant imparting agent. 2. The flame-retardant polyurethane foam according to claim 1, wherein the content of the brominated aromatic triazine compound is 5 to 50 parts by weight with respect to 100 parts by weight of the polyol. 3. A polyol obtained by adding 20% to 50% of polycaprolactone (PCL) to a polyfunctional polyether glycol, having an average molecular weight of 3000 to 5000 and a molecular weight distribution of 1.0 to 1.2, and a poly Characterized by comprising a urethane foam using a reaction product with an isocyanate as a material, containing a brominated aromatic triazine compound as a flame retardant, and containing a symmetric quaternary ammonium salt as a conductivity imparting agent. Conductive roll. 4. The flame-retardant polyurethane foam according to claim 3, wherein the content of the brominated aromatic triazine compound is 5 to 50 parts by weight with respect to 100 parts by weight of the polyol. 5. The polyol according to claim 3, wherein the content of the symmetrical quaternary ammonium salt is the polyol 10
0.05 to 20 parts by weight with respect to 0 parts by weight, a conductive roll imparted with flame retardancy. 6. A conductive roll according to claim 3, further containing conductive carbon black as a conductivity-imparting agent. 7. The flame-retardant property according to claim 6, wherein the content of the conductive carbon black is 0.5 to 5.0 parts by weight with respect to 100 parts by weight of the polyol. Conductive roll.