Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
  • C08G18/40—High-molecular-weight compounds
  • C08G18/61—Polysiloxanes
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/08—Processes
  • C08G18/10—Prepolymer processes involving reaction of isocyanates or isothiocyanates with compounds having active hydrogen in a first reaction step
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
  • C08G18/40—High-molecular-weight compounds
  • C08G18/42—Polycondensates having carboxylic or carbonic ester groups in the main chain
  • C08G18/4266—Polycondensates having carboxylic or carbonic ester groups in the main chain prepared from hydroxycarboxylic acids and/or lactones
  • C08G18/4269—Lactones
  • C08G18/4277—Caprolactone and/or substituted caprolactone

Definitions

• the present invention relates to a polyurethane elastomer which is particularly suitable for use on a cleaning blade of an electronic copying machine.
• This polyurethane elastomer has a small change in viscoelasticity (rubber elasticity) under a wide temperature range of atmosphere and an excellent low-temperature characteristic with glass transition temperature of -5 degrees C or lower.
• a cleaning blade is used for removing the toner which remains on the surface of photosensitive drums, such as the drums used in an electronic copying machine.
• Polyurethane elastomers are known as a material which is suitable for such applications.
• a polyurethane elastomer having high mechanical properties such as strength and elongation, that is elastic, and has low abrasive characteristics and excellent wear resistance is required.
• the locations which use (or install) electronic copying machines, such as a copy machine and fax, are not usually limited to the inside of buildings in which the environment is constantly adjusted to a normal temperature.
• JP-A-57-201275 describes a method for achieving a low friction coefficient of a polyurethane rubber by incorporating a fluorine-containing compound into the polyurethane rubber.
• JP-A-57-201276 describes a method for achieving a low friction coefficient of a polyurethane rubber by incorporating a polysiloxane oil in the polyurethane rubber.
• JP-A-5-224573 describes a method for obtaining a cleaning blade for electronic copying machine having a low coefficient of friction and excellent heat resistance by using a silicone-containing multi-components copolymer, and a saturated or unsaturated fatty acid amide. Since the amount of the polysiloxane diol used is small in this method, a polysiloxane chain hardly comes to the surface so that the effectiveness on low friction properties or physical properties is insufficient.
• JP-A-7-290601 describes a method for producing a cleaning blade having a low- friction layer by using a polysiloxane monool having a hydroxyl group at one end for a urethane rubber.
• the use of a polysiloxane monool results in a urethane composition having a lower molecular weight and decreased strength.
• JP-A-2003-186366 describes a method for obtaining an electronic copying- machine cleaning blade with excellent low-friction characteristics by using an organopolysiloxane having two primary hydroxyl groups at one end and no reactive group at the other end.
• a polysiloxane diol having two active hydrogen atoms at one end is insufficient, since disadvantageously a dimethylsilicone chain works as a side chain of a long chain and disturbs a molecular structure so that physical properties are deteriorated.
• the development of the polyurethane elastomer for cleaning blade of electronic copying machine achieving sufficiently the functions of cleaning blade is desired, which polyurethane elastomer has the small change of the viscoelasticity under a wide range of circumferential temperature, and excellent low-temperature characteristics including the glass transition temperature of not larger than -5 degrees C.
• One of objects of the present invention is to provide a polyurethane elastomer for a cleaning blade of an electronic copying machine which has a small temperature dependency even under a wide range of temperature conditions, a small change of viscoelasticity (rubber elasticity), a glass transition temperature of not larger than -5 degrees C, and excellent low-temperature characteristics.
• This and other objects which will be apparent to those skilled in the art are achieved by the polyurethane elastomer(s) described more fully below which are produced from a polyol component that includes a bifunctional silicone oil.
• the present invention is directed to a polyurethane elastomer useful for a cleaning blade of an electronic copying machine.
• This polyurethane elastomer is the reaction product of (1) a polyol component, (2) a chain extender, and (3) an isocyanate component.
• the polyol component includes a silicone oil which is bifunctional, has hydroxyl groups at both ends and contains an ester group.
• the isocyanate component includes an aromatic isocyanate.
• the silicone oil content is from about 5.0 to about 50% by weight, based on the weight of the polyurethane elastomer.
• the polyurethane elastomers of the present invention have a hardness of from 70 to 90 in shore A, a tan delta (10) value at 10 degrees C of 0.32 or less, and a tan delta (55) value at 55 degrees C of 0.02 or more in viscoelasticity with the difference between tan delta (10) and tan delta (55) being no greater than 0.30.
• the polyurethane elastomers of the present invention satisfy the mechanical characteristics, such as hardness, strength and elongation, necessary for a cleaning blade of electronic copying machine. These elastomers also have a small temperature dependence under a wide atmospheric temperature range, for example, the range from 10 to 55 degrees C, and viscoelasticity (rubber elasticity) at a low-temperature range below 10 degrees C due to the glass transition temperature of -5 degrees C or lower.
• the polyurethane elastomer from which a cleaning blade for an electronic copying machine is produced in accordance with the present invention is a reaction product of a polyol component (1), a chain extender (2), and an isocyanate component (3).
• the polyol component (1) contains a silicone oil having an ester group in the molecule and also having hydroxyl groups at both ends.
• the isocyanate component (2) contains an aromatic isocyanate.
• the polyurethane elastomer of the present invention has a Shore A hardness of 70 to 90, viscoelasticity tan ⁇ (10) at 10 degrees C of at most 0.32, and viscoelasticity tan ⁇ (55) at 55 degrees C of at least 0.02. The difference between ⁇ (10) and ⁇ (55) is at most 0.30.
• the use of a polyurethane elastomer having these properties for the cleaning blade of the electronic copying machine results in a cleaning blade which does not spoil the performance copying machine even under a wide range of atmospheric temperature conditions.
• the polyurethane elastomer used for a cleaning blade of an electronic copying machine in accordance with the present invention is preferably made with a polyol component that includes a silicone oil which contains an ester group in a molecule and which is difunctional (diol) having hydroxyl groups at both ends.
• the polyol component may be made up solely of the silicone oil.
• the use of a polyol component containing only the silicone oil is not preferred because such a polyol component would have a high price and be disadvantageous with respect to cost. It is preferred that the polyurethane elastomer be produced from a polyol component that includes the silicone oil and a polycaprolactone ester polyol having low-temperature characteristics superior to other polyester polyols.
• the silicone oil Because the silicone oil has hydroxyl groups at both ends, it reacts with the isocyanate component so that it is incorporated into a molecule, and does not produce a contamination which will bleed. Inclusion of the ester group can improve the compatibility with the isocyanate component. The product does not become cloudy when it is produced with the aromatic isocyanate and the isocyanate prepolymer. The physical properties of the polyurethane elastomer resulting therefrom preferably become uniform. The molecular weight of the silicone oil is preferably from 1,000 to 10,000, more preferably from 2,000 to 6,000.
• the silicone oil has a molecular weight of from 1,000 to 10,000
• the polyurethane elastomer produced from that oil will produce a cleaning blade for an electronic copying machine which advantageously has a hardness that is not too high and a suitable elasticity.
• the silicone oil used to produce the elastomers of the present invention may be formed from a silicone moiety and an ester moiety.
• silicone moiety means a moiety containing (1) a siloxane bond (Si-O), and (2) a hydrogen atom, an aliphatic group (1-30 carbon atoms) (especially an alkyl group), an aromatic group (6-30 carbon atoms) or an araliphatic group (7-30 carbon atoms) which is bonded (usually directly) to silicon or oxygen in the siloxane linkage.
• the silicone moiety is a moiety remaining after excluding the ester moiety from the silicone oil.
• the ester moiety means the organic acid moiety (namely, a moiety remaining after excluding a hydrogen atom from an organic acid) which forms an ester.
• the acid which forms an organic acid moiety is a fatty acid (preferably, a fatty acid having 2-30 carbon atoms).
• the silicone oil be a silicone oil in which a part of the methyl group of the dimethyl silicone oil has been replaced by a higher fatty acid ester.
• the higher fatty acid is a fatty acid having 10-30 carbon atoms.
• the silicone (especially one with a dimethyl siloxane group) content in the silicone oil is preferably from 30 to 70 % by weight, more preferably from 40 to 60 % by weight.
• the ester group content in the silicone oil is preferably from 30 to 70 % by weight, more preferably, from 40 to 60 % by weight.
• the "silicone content” means the weight % of the silicone moiety based on the silicone oil
• the "ester group content” means the weight % of the ester moiety based on the silicone oil
• ester group content is from 30 to 70% by weight, suitable physical properties, such as strength for the polyurethane elastomer for cleaning blade of electronic copying machine, are achieved.
• the content of the silicone oil in the polyurethane elastomer is preferably from
• silicone oil is even more preferred.
• silicone oil content is in the range from 5 to 50% by weight, the coefficient of friction of the polyurethane elastomer fora cleaning blade of electric copying machine will be small, and suitable physical properties will be acquired.
• a polycaprolactone ester polyol as the polyol component in addition to the silicone oil.
• suitable polycaprolactone ester polyols include polycaprolactone ester polyols having an average functionality of 2 to 3 and an average molecular weight of 500 to 3,000.
• Such polycaprolactone ester polyols can be prepared by ring-opening polymerization of epsilon-caprolactone with an initiator, for example, a glycol such as ethylene glycol, diethylene glycol, dipropylene glycol or a triol such as glycerol, trimethylol propane or trimethylol ethane.
• an initiator for example, a glycol such as ethylene glycol, diethylene glycol, dipropylene glycol or a triol such as glycerol, trimethylol propane or trimethylol ethane.
• a polycaprolactone ester polyol having an average functionality of 2 to 3 and an average molecular weight of 2,000 to 3,000 is preferred.
• a diol having a functionality of 2 and an average molecular weight of 2,000 to 3,000 More preferred is a diol having a functionality of 2 and an average molecular weight of 2,000 to 2,500.
• the elasticity of the polyurethane elastomer is decreased, if the average molecular weight is smaller than 500. If the average molecular weight is larger than 3,000, an isocyanate prepolymer prepared by reacting the aromatic isocyanate with the polyol has high viscosity so that the workability worsens.
• the polycaprolactone ester polyol may be used alone or in combination with other such polyols.
• Suitable amounts of the polycaprolactone ester polyol are preferably from 8.0% to 70% by weight, more preferably from 10.0% to 65 % by weight, based on the polyurethane elastomer.
• silicone oil content of the polyol component is in the range of 5 to
• the polyurethane elastomer for a cleaning blade of an electric copying machine has a glass transition temperature of at most -5 degrees C, little temperature dependence and a variation of tan delta value which is at most 0.30 at the temperature range between 10 degrees C and 55 degrees C.
• the silicone oil and the polycaprolactone ester polyol may be used by mixing either with other materials in the polyol component or with the isocyanate component. They may be mixed with both other materials in the polyol component and with the isocyanate component.
• the NCO content of the silicone oil- and the polycaprolactone ester polyol- containing NCO-terminated prepolymer is preferably from 8% to 25%, more preferably from 10% to 20%.
• the viscosity is preferably from 100 mPas to 3,000 mPas at 70 degrees C, more preferably, from 400 to 2,000 mPas at 70 degrees C.
• the viscosity range of 100 to 3,000 mPas at 70 degrees C is advantageous because workability of the prepolymer is relatively easy.
• aromatic isocyanates useful as the isocyanate component include 4,4'-diphenyl methane diisocyanate (MDI), toluene diisocyanate (TDI), carbodiimide-modified MDI, polymethylene polyphenylene polyisocyanate (polymeric MDI) and naphthylene diisocyanate (NDI). These may be used alone or in combination. Among these, MDI is preferred.
• chain extender conventionally known low-molecular weight hydroxy compounds can be used.
• suitable chain extenders include: glycols such as 1,4-butane diol, 1,6-hexane diol, ethylene glycol, diethylene glycol and neopentyl glycol; polyhydric alcohols having valence of three or more, such as trimethylol propane, glycerol, diglycerol and pentaerythritol; and amino polyhydric alcohols such as diisopropanol amine, triisopropanol amine and triethanol amine. Glycols and trihydric alcohols are preferred.
• the amount of the chain extender may be from 1% to 50 % by weight, preferably, from 3% to 20 % by weight, based on the polyurethane elastomer.
• urethanization catalysts fillers, coloring agents and antioxidants, etc. can be included in the polyol component or used in addition to the polyol component and the chain extender.
• Dimethyl polysiloxane having a viscosity of 350 to 12,500 mPa.s at 25 degrees C can be used as an antifoaming agent, in an amount of 0.001% to 0.02% by weight based on the polyurethane elastomer.
• Dimethyl polysiloxane may be used in the formulated polyol side, and since dimethyl polysiloxane does not react with isocyanate, dimethyl polysiloxane may also be used in the isocyanate component side.
• dimethyl polysiloxane eliminates the bubbles of a mixture between the formulated polyol and the isocyanate component when preparing the polyurethane elastomer, the formation of large bubbles on the polyurethane elastomer is eliminated and the decrease of strength due to the presence of such bubbles is avoided.
• the coefficient of friction becomes small due to the lubricity of dimethyl polysiloxane.
• the mixing ratio of the formulated polyol to the isocyanate component is preferably from 0.95 to 1.15, more preferably, from 1.05 to 1.10.
• the polyurethane elastomer for a cleaning blade of an electronic copying machine of the present invention is preferably not foamed and is prepared without using a blowing agent such as water.
• the density of the polyurethane elastomer is preferably 1.00 g/cm 3 or more.
• the lack of foaming can easily give the viscoelasticity suitable for the polyurethane elastomer for a cleaning blade of an electronic copying machine, because a urea bond will not be generated, for example, by the reaction of water and the isocyanate component.
• the density of at least 1.00 g/cm 3 can give the low-friction and mechanical properties suitable for a polyurethane elastomer to be used for a cleaning blade of an electronic copying machine.
• the polyurethane elastomer increases the volume to decrease the density, it is hard to obtain the desired low friction, since the silicone oil will be dispersed in the polyurethane elastomer and the amount of silicone oils on the surface of the polyurethane elastomer is decreased.
• the polyurethane elastomers prepared in the above-described manner with the above-described materials have a hardness by Shore A of 70-90, a tan delta value of at most 0.32 at 10 degrees C, a tan delta value of at least on 0.02 at 55 degrees C, and little temperature dependency because the variation range of the tan delta value is at most 0.30 at a wide range of atmospheric temperatures (for example, between 10 degrees C and 55 degrees C).
• the polyurethane elastomer since the glass transition temperature is at most -5 degrees C, the polyurethane elastomer has excellent low-temperature characteristics, good viscoelasticity even at the low-temperature range of at most 10 degrees C.
• the product polyurethane elastomer is the optimal polyurethane elastomer for a cleaning blade of an electronic copying machine which can be used under various atmosphere temperatures.
• X22- 6132 a bifunctional silicone oil with OH number of 25 mg KOH/g, MW of about 4,500, silicone content of 40%, ester group content of 60%, two OH-groups at the ends, manufactured by Shin-Etsu Chemical Co., Ltd.
• SH200 as antifoaming agent dimethylpolysiloxane manufactured by Toray Silicone Co., Ltd., viscosity: 1,000 mPas at 25 degrees C
• the resultant mixture was reacted at 80 degrees C for 4 hours.
• the resultant NCO-terminated prepolymer (B) had an NCO content of 16% and a viscosity of 420 mPas at 70 degrees C. Further, turbidity such as white turbidity was hardly observed.
• PCL220 a difunctional polycaprolactone ester polyolwith an OH number of 56 mgKOH/g, MW of about 2,000, manufactured by Daicel Chemical Industries, Ltd.
• SH200 as antifoaming agent dimethylpolysiloxane manufactured by Toray Silicone Co., Ltd., viscosity: 1,000 mPas at 25 degrees C
• the resultant mixture was reacted at 80 degrees C for 4 hours.
• the resultant NCO-terminated prepolymer (A) had an NCO content of 13% and a viscosity of 580 mPas at 70 degrees C.
• a test sample (film) for measuring viscoelasticity having a thickness of 10 mil was prepared in such a way that the mixed liquid was poured in a mold under the same conditions as were used to prepare the molding by the above-described procedure. A blade was dragged without closing a lid.
• Test sample size for measurement 10 x 20 x 0.254 mm (10 mil thickness)
• a DMS-220 model manufactured by Seikoh Chemicals Co., Ltd was used to measure viscoelasticity at a frequency of 10 Hz in a temperature range of -60 degrees C to 80 degrees C, raising the temperature at a rate of 2 degrees C/min, to measure a peak temperature and tan delta at the glass transition temperature, and tan delta at 10 to 55 degrees C.
• tan delta is an index showing viscoelasticity in a test method for measuring viscoelasticity (in accordance with JIS K7244).
• the state of viscoelasticity change was determined from the range of change in tan delta value at 10 to 55 degrees C. It has been determined that when the range of change in the tan delta value is within 0.30, the change of viscoelasticity is small and is good (superior). When the change of viscoelasticity is large (i.e., more than 0.30), it is bad (inferior).
• Example 1 As shown in Table 1, a silicone oil, PCL220 and a chain extender were mixed so that the silicone oil was 14.1 wt% and PCL220 was 70.5 wt% in a formulated polyol.
• silicone oil and a chain extender were mixed so that silicone oil was 45.5 wt% in a formulated polyol.
• 100 g of the formulated polyol and 22.7 g of the NCO-terminated prepolymer (A) were mixed and stirred to undergo curing reaction, a molded article of polyurethane elastomer was prepared in such a way that the content of the silicone oil was 37.1 wt% and the content of PCL was 10.0 wt%.
• the resultant polyurethane elastomer had good viscoelasticity with a hardness of 84 in Shore A, a glass transition temperature of -8.0 degrees C, and a tan delta value at 10 degrees C of 0.164, and the range of change in tan delta value at 10 to 55 degrees C was 0.102.
• polyurethane elastomer having an excellent low-temperature performance and small temperature dependence with the range of change in tan delta value at 10 to 55 degrees C of at most 0.30, was obtained.
• PCL 220 and a chain extender were mixed so that PCL220 was 84.4 wt% in a formulated polyol.
• 100 g of the formulated polyol and 77 g of the NCO-terminated prepolymer (B) were mixed and stirred to undergo curing reaction, a molded article of polyurethane elastomer was prepared in such a way that the content of silicone oil was 21.5 wt% and the content of PCL was 47.7 wt%.
• the resultant polyurethane elastomer had good viscoelasticity with a hardness of 78 in Shore A, a glass transition temperature of -5.4 degrees C, and a tan delta value at 10 degrees C of 0.299, and the range of change in tan delta value at 10 to 55 degrees C was 0.263.
• the polyurethane elastomer having an excellent low-temperature performance and small temperature dependence with the range of change in tan delta value at 10 to 55 degrees C of at most 0.30, was obtained.
• Comparative Example 1 A molded article of polyurethane elastomer was prepared in such a way that neither a formulated polyol nor an isocyanate component was mixed with a silicone oil.
• the resultant polyurethane elastomer had insufficient viscoelasticity with a hardness of 85 in Shore A, a glass transition temperature of -2.0 degrees C, and a tan delta value at 10 degrees C of 0.391, and had large temperature dependence with the range of change in tan delta value at 10 to 55 degrees C of as large as 0.362.
• Preferred applications for the polyurethane elastomer of the present invention since temperature dependence is small, particularly excellent in elasticity at low temperature range, are listed blades or rolls for cleaning and the like of electronic copying machines such as a facsimile machine, a copier and a printer because they are suitable for use under various atmospheric temperatures.

Landscapes

• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Polyurethanes Or Polyureas (AREA)
• Cleaning In Electrography (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=39350239

Family Applications (1)

Country Status (4)

Families Citing this family (6)

Citations (3)

Family Cites Families (10)

• 2007
  • 2007-02-27 JP JP2007047211A patent/JP5110908B2/ja not_active Expired - Fee Related
• 2008
  • 2008-02-19 WO PCT/EP2008/001251 patent/WO2008104300A1/en not_active Ceased
  • 2008-02-25 US US12/072,178 patent/US20080249277A1/en not_active Abandoned
  • 2008-02-26 TW TW097106530A patent/TW200900427A/zh unknown

Patent Citations (3)

Non-Patent Citations (2)

Also Published As

Similar Documents

Legal Events