A method for separating low molecular weight impurities from perfluoroether elastomer emulsion

Abstract

The present application provides a method for separating low molecular weight impurities from a perfluoroether elastomer emulsion, which is applied to the technical field of perfluoroether elastomers, including: S1, preparing a perfluoroether elastomer emulsion containing micro-nano bubbles, wherein the gas in the perfluoroether elastomer emulsion containing micro-nano bubbles accounts for 2-10% of the volume of the gas-liquid mixture; S2, centrifuging the perfluoroether elastomer emulsion containing micro-nano bubbles using a centrifugal separator to obtain a perfluoroether elastomer agglomerate and a residual liquid containing impurities, and the inner wall of the centrifugal separator is provided with a hydrophobic varnish; S3, washing and drying the perfluoroether elastomer agglomerate to obtain a perfluoroether elastomer. The present application prepares a perfluoroether elastomer by a method for separating low molecular weight impurities from a perfluoroether elastomer emulsion, and its composition is applied to semiconductor processes.

Description

Technical Field

[0001] The present application relates to the technical field of perfluoroether elastomer synthesis, and in particular to a method for separating low molecular weight impurities from a perfluoroether elastomer emulsion. Background Art

[0002] Fluorine-containing elastomers are mostly obtained by emulsion polymerization of various fluoroolefins. The emulsion polymerization synthesizes perfluoroether elastomers to obtain an emulsion containing perfluoroether elastomer. After degassing, the solid content of the emulsion is usually 20-35%, and the particle size of the perfluoroether elastomer in the emulsion ranges from 0.1 to 1μm. The emulsion composition is complex, mainly including: perfluoroether elastomer obtained by monomer polymerization, emulsifier, initiator, pH regulator, chain transfer agent, low molecular weight polymer and water. Some of these components must be removed during flocculation, washing, drying and other processes to avoid affecting the performance of the final product.

[0003] With the improvement of production technology and the development of fluorine chemistry and fluorine chemical industry, the adverse effects of a certain component in the final product can be reduced by adjusting the components of the formula. For example, the initiator uses an organic peroxide initiator azobisisobutyronitrile AIBN or diisopropyl peroxide dicarbonate IPP, the chain transfer agent uses a component consistent with the vulcanization point monomer such as diiodinated alkane, and the pH adjuster uses acetic acid or succinic acid. In recent years, based on the requirements of environmental protection and rational use of resources, emulsifiers with reactive functional groups are used to form composite dispersants such as fluorocarbon surfactants with reactive functional groups and ethylene glycol monomethyl ether composite dispersants, which mainly enrich the fluorine element in the core-shell of the emulsion, thereby reducing the amount of fluorine monomer while maintaining the original physical and chemical properties of organic fluorine polymers.

[0004] Low molecular weight polymer impurities formed by azobisisobutyronitrile in the initiator, diiodinated alkanes in the chain transfer agent and components in the composite dispersant such as ethylene glycol monomethyl ether are easy to form white flocs mixed with a small amount of elastomer in the flocculation process and mix in the product. This part of impurities must be effectively removed.

[0005] Based on this, the present invention provides a new technical solution. Summary of the invention

[0006] In view of this, the present specification provides a method for separating low molecular weight impurities from a perfluoroether elastomer emulsion. The method comprises:

[0007] S1, preparing a perfluoroether elastomer emulsion containing micro-nano bubbles, wherein the gas in the perfluoroether elastomer emulsion containing micro-nano bubbles accounts for 2-10% of the volume of the gas-liquid mixture;

[0008] S2, centrifugally separating the perfluoroether elastomer emulsion containing micro-nano bubbles by using a centrifugal separator to obtain a perfluoroether elastomer agglomerate and a residual liquid containing impurities, wherein a hydrophobic varnish is arranged on the inner wall of the centrifugal separator;

[0009] S3, washing and drying the perfluoroether elastomer agglomerate to obtain a perfluoroether elastomer.

[0010] Optionally, the perfluoroether elastomer emulsion containing micro-nano bubbles is formed by mixing deionized water with perfluoroether elastomer emulsion after generating micro-nano bubbles.

[0011] Optionally, the hydrophobic varnish cloth is hydrophobic polytetrafluoroethylene, polypropylene or polyvinylidene fluoride.

[0012] Optionally, in S2, the centrifugal factor of the centrifugal separator is It is 5000-20000.

[0013] Optionally, the temperature for centrifuging the perfluoroether elastomer emulsion containing micro-nano bubbles is 30-80°C.

[0014] Optionally, the surface of the varnished cloth is a smooth surface, or is provided with holes or grooves.

[0015] Optionally, the perfluoroether elastomer emulsion containing micro-nano bubbles is fed from the bottom of a centrifugal separator, the centrifugal residual liquid containing impurities is discharged from the top of the centrifugal separator, and the perfluoroether elastomer agglomerates are distributed on the surface of the varnished cloth.

[0016] Optionally, the particle size of the micro-nano bubbles in the perfluoroether elastomer emulsion containing micro-nano bubbles is less than 100 μm.

[0017] Optionally, the gas used to generate the micro-nano bubbles is air, carbon dioxide or nitrogen.

[0018] Optionally, the perfluoroether elastomer coacervate is washed with deionized water at 60-95°C.

[0019] Compared with the prior art, the at least one technical solution adopted in the embodiments of this specification can achieve the following beneficial effects:

[0020] The technical solution of the present application disperses micro-nano bubbles into a perfluoroether elastomer emulsion, and has hydrophobic or amphiphilic low molecular weight impurities and perfluoroether elastomers, and the hydrophobic part thereof adheres to the micro-nano bubbles, and the low molecular weight impurities have a large specific surface area, and a relatively large proportion of adhered micro-nano bubbles per unit volume, so that the density of the low molecular weight impurities becomes relatively small, and under the action of the same centrifugal force, the impurities move radially toward the center of the centrifugal device faster, thereby being separated from the perfluoroether elastomer;

[0021] After the perfluoroether elastomer is demulsified and condensed on the surface of the hydrophobic varnished cloth, a new hydrophobic surface is formed, which creates conditions for the perfluoroether elastomer to form a coagulation body. Finally, a large amount of low molecular weight impurities are dispersed in the centrifugal residual liquid, and a small amount of low molecular weight impurities are dispersed on the surface of the perfluoroether elastomer. Deionized water is used for washing, thereby reducing the content of low molecular weight impurities in the perfluoroether elastomer. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, they can also refer to these attached process schematic diagrams without paying any creative work.

[0023] Figure 1 This is a process schematic diagram of a method for separating low molecular weight impurities from a perfluoroether elastomer emulsion in the present application. DETAILED DESCRIPTION

[0024] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0025] The following describes the implementation methods of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The present application can also be implemented or applied through other different specific implementation methods, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, in the absence of conflict, the following embodiments and the features in the embodiments can be combined with each other. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work belong to the scope of protection of the present application.

[0026] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structures and / or functions described herein are merely illustrative. Based on the present application, it should be understood by those skilled in the art that an aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. In addition, in the following description, specific details are provided to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that it can be practiced without these specific details.

[0027] Fluorine-containing elastomers are mostly obtained by emulsion polymerization of various fluoroolefins. Emulsion polymerization is used to synthesize perfluoroether elastomers to obtain perfluoroether elastomer emulsions. After degassing, the solid content of the emulsion is usually 20-35%, and the particle size of the perfluoroether elastomer in the emulsion ranges from 0.1 to 1 μm. The emulsion composition is complex, mainly including: perfluoroether elastomer obtained by monomer polymerization, emulsifier, initiator, pH regulator, chain transfer agent, low molecular weight polymer and water. Some of these components must be removed during flocculation, washing, drying and other processes to avoid affecting the performance of the final product.

[0028] With the improvement of production technology and the development of fluorine chemistry and fluorine chemical industry, the adverse effects of a certain component in the final product can be reduced by adjusting the components of the formula. For example, the initiator uses an organic peroxide initiator azobisisobutyronitrile AIBN or diisopropyl peroxide dicarbonate IPP, the chain transfer agent uses a component consistent with the vulcanization point monomer such as diiodinated alkane, and the pH adjuster uses acetic acid or succinic acid. In recent years, based on the requirements of environmental protection and rational use of resources, emulsifiers with reactive functional groups are used to form composite dispersants such as fluorocarbon surfactants with reactive functional groups and ethylene glycol monomethyl ether composite dispersants, which mainly enrich the fluorine element in the core-shell of the emulsion, thereby reducing the amount of fluorine monomer while maintaining the original physical and chemical properties of organic fluorine polymers.

[0029] Low molecular weight polymer impurities formed by azobisisobutyronitrile in the initiator, diiodinated alkanes in the chain transfer agent and components in the composite dispersant such as ethylene glycol monomethyl ether are easy to form white flocs mixed with a small amount of elastomer in the flocculation process and mix in the product. This part of impurities must be effectively removed.

[0030] Based on this, the present specification proposes a method for separating low molecular weight impurities from a perfluoroether elastomer emulsion, comprising:

[0031] S1. preparing a perfluoroether elastomer emulsion containing micro-nano bubbles, wherein the gas in the perfluoroether elastomer emulsion containing micro-nano bubbles accounts for 2-10% of the volume of the gas-liquid mixture;

[0032] S2, centrifugally separating the perfluoroether elastomer emulsion containing micro-nano bubbles by using a centrifugal separator to obtain a perfluoroether elastomer agglomerate and a residual liquid containing impurities, and setting a hydrophobic varnish cloth on the inner wall of the centrifugal separator;

[0033] S3, washing and drying the perfluoroether elastomer agglomerate to obtain a perfluoroether elastomer.

[0034] In step S1, the perfluoroether elastomer emulsion containing micro-nano bubbles is formed by mixing the micro-nano bubbles generated by deionized water with the perfluoroether elastomer emulsion, and the micro-nano bubbles in the deionized water are generated by a pressure vessel method, a membrane method or a cyclone method.

[0035] The particle size of the micro-nano bubbles in the perfluoroether elastomer emulsion containing micro-nano bubbles is less than 100 μm. The gas used to generate the micro-nano bubbles is air, carbon dioxide or nitrogen.

[0036] In step S2, the hydrophobic varnish cloth is hydrophobic polytetrafluoroethylene, polypropylene or polyvinylidene fluoride. Centrifugal factor of centrifugal separator The ratio of the perfluoroether elastomer to the varnish cloth is 5000-20000, the surface of the varnish cloth is a smooth surface or is provided with holes or grooves, the perfluoroether elastomer emulsion containing micro-nano bubbles is fed from the bottom of the centrifuge, the centrifugal residual liquid containing impurities is discharged from the top of the centrifuge, and the perfluoroether elastomer agglomerates are distributed on the surface of the varnish cloth.

[0037] In the present application, the temperature during the centrifugal separation process of the perfluoroether elastomer emulsion containing micro-nano bubbles is 30-80°C.

[0038] In the present application, the perfluoroether elastomer agglomerate is washed with deionized water at 60-95°C.

[0039] In the examples and comparative examples of the present application, the ratio of the volume of deionized water used to generate micro-nano bubbles to the volume of the emulsion is 2:1.

[0040] Preparation Example of Perfluoroether Elastomer Emulsion

[0041] The preparation of the perfluoroether elastomer emulsion comprises the following steps: step 1, in a microreactor equipped with a stirrer, 100 g of sodium perfluorooctanoate and 20 g of ethylene glycol monomethyl ether are stirred for 0.2 h at a speed of 10000 rpm to obtain a composite dispersant microemulsion for standby use;

[0042] Step 2: In a 50 L stainless steel reactor, add 32 kg of deionized water, deoxygenate to an oxygen content of less than or equal to 10 ppm, add 60 g of the composite dispersant microemulsion obtained in step (1), 30 g of disodium hydrogen phosphate, and 30 g of 4-bromo-3,3,4,4-tetrafluorobutene, and stir at 40 rpm for 10 min;

[0043] Step 3, raising the temperature of the above reactor to 70°C, adding 11 kg of a mixed monomer with a molar ratio of tetrafluoroethylene:perfluoromethyl vinyl ether = 60:40 until the pressure of the reactor is 2.5 MPa, adding 20 g of ammonium persulfate to the reactor through nitrogen, and starting a polymerization reaction. During the reaction, a mixed monomer with a molar ratio of tetrafluoroethylene:perfluoromethyl vinyl ether = 60:40 is continuously added by a compressor to maintain the reaction pressure at 2.5 MPa. When the conversion rate of the mixed monomer reaches 30%, 30 g of 1,4-diiodoperfluorobutane is added to the reactor through nitrogen;

[0044] Step 4: When the solid content of the emulsion in the reactor reaches 28%, the reaction is stopped, and the unreacted monomers are recovered to obtain a perfluoroether elastomer emulsion of a peroxide crosslinking system.

[0045] The reagents used in this protocol are as follows:

[0046] Sodium perfluorooctanoate, Shanghai Lanrun Chemical Co., Ltd.;

[0047] Ethylene glycol monomethyl ether, Anhui Erbang Chemical Co., Ltd.;

[0048] Disodium hydrogen phosphate, Weifang Pengchuang Chemical Co., Ltd.;

[0049] 4-Bromo-3,3,4,4-tetrafluorobutene, Shanghai Huayuan Century Trading Co., Ltd.;

[0050] Ammonium persulfate, Wujiang Yongli Chemical Co., Ltd.;

[0051] 1,4-Diiodoperfluorobutane, Hubei Xinhongli Chemical Co., Ltd.

[0052] The object of emulsion impurity removal in this application is the perfluoroether elastomer emulsion synthesized in the above steps as an example.

[0053] Example 1

[0054] S1. A perfluoroether elastomer emulsion containing micro-nano bubbles is formed by generating micro-nano bubbles in deionized water and mixing them with an emulsion (the emulsion synthesized in the preparation example). The gas-liquid mixing volume ratio in the emulsion is 2%, and the gas used by the micro-nano bubbles is air.

[0055] S2. The perfluoroether elastomer emulsion containing micro-nano bubbles was centrifugally separated by a centrifugal separator, and the feed rate was 50 L / h for 6 min to obtain the perfluoroether elastomer agglomerate and the residual liquid containing impurities. The inner wall of the centrifugal separator was set with a hydrophobic varnish cloth as smooth polytetrafluoroethylene, and the centrifugal factor of the centrifugal separator was The ratio of the perfluoroether elastomer to the varnish is 5000, the perfluoroether elastomer emulsion containing micro-nano bubbles is fed from the bottom of the centrifugal separator, the centrifugal residual liquid containing impurities is discharged from the top of the centrifugal separator, and the perfluoroether elastomer agglomerates are distributed on the surface of the varnished cloth;

[0056] S3. Washing and drying the perfluoroether elastomer agglomerate to obtain the perfluoroether elastomer.

[0057] In this scheme, the temperature for centrifugal separation of the perfluoroether elastomer emulsion containing micro-nano bubbles is 40 °C; and it is washed with deionized water at 85 °C for 3 h.

[0058] Example 2

[0059] S1. The perfluoroether elastomer emulsion containing micro-nano bubbles is formed by generating micro-nano bubbles in pure water and mixing them with an emulsion (the emulsion synthesized in the preparation example), wherein the gas-liquid mixing volume ratio in the emulsion is 4%, and the gas used for the micro-nano bubbles is nitrogen;

[0060] S2. The perfluoroether elastomer emulsion containing micro-nano bubbles was centrifugally separated by a centrifugal separator, and the feed rate was 50 L / h for 6 min to obtain the perfluoroether elastomer agglomerate and the residual liquid containing impurities. The inner wall of the centrifugal separator was provided with a hydrophobic varnished cloth, which was a hydrophobic 10-mesh polytetrafluoroethylene varnished cloth (pore size 1.7 mm). The centrifugal factor of the centrifugal separator was is 10000, the perfluoroether elastomer emulsion containing micro-nano bubbles is fed from the bottom of the centrifugal separator, the centrifugal residual liquid containing impurities is discharged from the top of the centrifugal separator, and the perfluoroether elastomer agglomerates are distributed on the surface of the varnished cloth;

[0061] S3. Washing and drying the perfluoroether elastomer agglomerate to obtain the perfluoroether elastomer.

[0062] In this scheme, the centrifugal separation temperature of the perfluoroether elastomer emulsion containing micro-nano bubbles is 60 °C; and it is washed with deionized water at 85 °C for 3 h.

[0063] Example 3

[0064] S1. The perfluoroether elastomer emulsion containing micro-nano bubbles is formed by generating micro-nano bubbles in pure water and mixing them with an emulsion (the emulsion synthesized in the preparation example), wherein the gas-liquid mixing volume ratio in the emulsion is 8%, and the gas used for the micro-nano bubbles is nitrogen;

[0065] S2. The perfluoroether elastomer emulsion containing micro-nano bubbles was centrifuged by a centrifugal separator, and the feed rate was 50 L / h for 6 min to obtain the perfluoroether elastomer agglomerate and the residual liquid containing impurities. The inner wall of the centrifugal separator was provided with a hydrophobic varnish cloth, which was a hydrophobic 10-mesh polyvinylidene fluoride varnish cloth (pore size 1.7 mm). The centrifugal factor of the centrifugal separator was 1.5. The pressure is 18000, the perfluoroether elastomer emulsion containing micro-nano bubbles is fed from the bottom of the centrifugal separator, the centrifugal residual liquid containing impurities is discharged from the top of the centrifugal separator, and the perfluoroether elastomer agglomerates are distributed on the surface of the varnished cloth;

[0066] S3. Washing and drying the perfluoroether elastomer agglomerate to obtain the perfluoroether elastomer.

[0067] In this scheme, the centrifugal separation temperature of the perfluoroether elastomer emulsion containing micro-nano bubbles is 60 °C; and it is washed with deionized water at 95 °C for 3 h.

[0068] Example 4

[0069] The difference between this embodiment and embodiment 2 is that the centrifugal factor of the centrifugal separation is is 12000.

[0070] Example 5

[0071] The difference between this embodiment and embodiment 2 is that the temperature during the centrifugal separation and washing process of the perfluoroether elastomer emulsion containing micro-nano bubbles is 85°C.

[0072] Comparative Example 1

[0073] The difference between this comparative example and Example 2 is that the centrifugally separated emulsion does not contain micro-nano bubbles.

[0074] Comparative Example 2

[0075] The difference between this comparative example and Example 2 is that a hydrophilic polytetrafluoroethylene varnished cloth is provided on the inner wall of the centrifugal separator.

[0076] Preparation of test samples

[0077] About 350 g of the perfluoroether elastomer agglomerate soaked and washed in deionized water was taken and dried in an oven at 120° C. for 3 h; about 324-336 g of dry perfluoroether elastomer was obtained.

[0078] 2.0% (relative to the mass of dry perfluoroether elastomer) of 2,5-dimethyl-2,5-bis(tert-butyl peroxide) hexane vulcanizing agent and 3% (relative to the mass of dry perfluoroether elastomer) of triallyl isocyanurate (TAIC) vulcanizing aid were added and mixed to obtain a compound rubber.

[0079] The compression molding conditions were 8 MPa, 160 °C, 6 min, and the secondary vulcanization conditions were 220 °C, 6 h. An O-ring (type 214) with a wire diameter of 3.53 mm and an inner diameter of 24.99 mm was obtained for testing.

[0080]

[0081] By comparing Example 2 with Examples 3 and 4, it can be seen that although the coagulates of both have no white spots, the thickness of the coagulate at the feed point of Example 3 is greater than that of Example 2, and the metal ion content in Example 3 is lower than that in Example 2, which means that the higher the centrifugal factor, the easier it is for the coagulates to be separated and enriched, and the lower the content of low molecular weight impurities in the perfluoroether elastomer; as the temperature of the centrifugal separation of the perfluoroether elastomer emulsion and the washing temperature increase, the content of low molecular weight impurities in the perfluoroether elastomer decreases.

[0082] By comparing Example 2 with Comparative Example 1, it can be seen that both the agglomerate and the sealing ring in Comparative Example 1 have white spots, indicating that it is difficult to effectively separate low molecular weight impurities in the absence of micro-nano bubbles. Since low molecular weight impurities have a large specific surface area and a relatively large proportion of adhered micro-nano bubbles per unit volume, they are separated from the perfluoroether elastomer under the action of centrifugal force, thereby achieving the removal of low molecular weight impurities.

[0083] By comparing Example 2 and Comparative Example 2, it can be seen that due to the hydrophobicity of perfluoroether elastomer, the perfluoroether elastomer cannot achieve demulsification and coagulation on the surface of the hydrophilic varnished cloth, and can only play a concentrating role, making it difficult to separate low molecular weight impurities from the perfluoroether elastomer.

[0084] In this specification, the same or similar parts between the various embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the embodiments described later, the description is relatively simple, and the relevant parts can be referred to the partial description of the previous embodiments.

[0085] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A method for separating low molecular weight impurities from a perfluoroether elastomer emulsion, characterized in that: include S1, preparing a perfluoroether elastomer emulsion containing micro-nano bubbles, wherein the gas in the perfluoroether elastomer emulsion containing micro-nano bubbles accounts for 2-10% of the volume of the gas-liquid mixture; S2, centrifugally separating the perfluoroether elastomer emulsion containing micro-nano bubbles by using a centrifugal separator to obtain a perfluoroether elastomer agglomerate and a residual liquid containing impurities, wherein a hydrophobic varnish is arranged on the inner wall of the centrifugal separator; S3, washing and drying the perfluoroether elastomer agglomerate to obtain a perfluoroether elastomer.

2. The method for separating low molecular weight impurities from a perfluoroether elastomer emulsion according to claim 1, characterized in that: The perfluoroether elastomer emulsion containing micro-nano bubbles is formed by mixing micro-nano bubbles generated in deionized water with the perfluoroether elastomer emulsion.

3. The method for separating low molecular weight impurities from a perfluoroether elastomer emulsion according to claim 1, characterized in that: The hydrophobic varnish cloth is hydrophobic polytetrafluoroethylene, polypropylene or polyvinylidene fluoride.

4. The method for separating low molecular weight impurities from a perfluoroether elastomer emulsion according to claim 1, characterized in that: In S2, the centrifugal factor of the centrifugal separator It is 5000-20000.

5. The method for separating low molecular weight impurities from a perfluoroether elastomer emulsion according to claim 1, characterized in that: The temperature for centrifuging the perfluoroether elastomer emulsion containing micro-nano bubbles is 30-80°C.

6. The method for separating low molecular weight impurities from a perfluoroether elastomer emulsion according to claim 1, characterized in that: The surface of the varnished cloth is a smooth surface, or is provided with holes or grooves.

7. The method for separating low molecular weight impurities from a perfluoroether elastomer emulsion according to claim 1, characterized in that: The perfluoroether elastomer emulsion containing micro-nano bubbles is fed from the bottom of a centrifugal separator, the residual liquid containing impurities is discharged from the top of the centrifugal separator, and the perfluoroether elastomer agglomerates are distributed on the surface of the varnished cloth.

8. The method for separating low molecular weight impurities from a perfluoroether elastomer emulsion according to claim 1, characterized in that: The particle size of the micro-nano bubbles in the perfluoroether elastomer emulsion containing micro-nano bubbles is less than 100 μm.

9. The method for separating low molecular weight impurities from a perfluoroether elastomer emulsion according to claim 1, characterized in that: The gas used to generate micro-nano bubbles is air, carbon dioxide or nitrogen.

10. The method for separating low molecular weight impurities from a perfluoroether elastomer emulsion according to claim 1, characterized in that: The perfluoroether elastomer agglomerate is washed with deionized water at 60-95°C.

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