JPS6320854B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a silicone fluid, particularly a silicone fluid in which both ends of the molecular chain are blocked with a cyclic diorganopolysiloxane.
This invention relates to a silicone fluid with excellent low-temperature flow characteristics. (Prior art) It is already well known that dimethyl silicone oil has a smaller temperature coefficient and superior low-temperature flow characteristics than various vegetable oils, animal oils, mineral oils, etc. It is also known that compounds having a small amount of phenyl, fluoropropyl, isobutyl, etc. introduced into the unit, or a branched structure introduced into the molecule exhibit better low-temperature flow characteristics. However, products whose low-temperature flow properties are improved by introducing a small amount of organic groups into dimethylpolysiloxane units have a larger temperature coefficient than dimethylsilicone oils, so their properties are intermediate between mineral oils and dimethylsilicone oils. Therefore, this type of silicone oil has a temperature coefficient equal to that of dimethyl silicone, which is -100.
There is a desire for something that can be used as an oil even at ℃. (Structure of the Invention) The present invention relates to a silicone fluid with excellent low-temperature flow characteristics that can meet these demands. [Here, R ¹ is the same or different group selected from an alkyl group having 1 to 8 carbon atoms, a vinyl group, a phenyl group, and a fluoroalkyl group having 3 to 10 carbon atoms,
R ² is the formula

[Formula] (where Q is a divalent hydrocarbon group, a heteroatom-containing divalent hydrocarbon group having 1 to 6 carbon atoms, l is an integer of 3 to 6),
n is an integer of 5 to 50 or less]. In other words, the present inventors have conducted various studies on organopolysiloxanes that do not crystallize and exhibit low-temperature flow characteristics even below -50°C, and have found that if both ends of a normal organopolysiloxane are capped with cyclic diorganopolysiloxy groups, this can be achieved. After discovering that the crystallization temperature can be lowered and proceeding with research on this, we created a cyclic diorganopolysiloxy group with the formula shown above. (R ¹ and Q are the same as above) and if this fluid has a degree of polymerization of 5 to 50 or less, it will have no crystallization point or melting point. The present invention was completed by confirming that the low-temperature properties can be significantly improved, and that this product exhibits excellent flow properties even at -100°C. The organopolysiloxane forming the silicone fluid of the present invention can be obtained by substituting the terminal group of a conventional diorganopolysiloxane with the above-mentioned cyclic diorganopolysiloxy group. The organopolysiloxane is preferably one in which both ends of the molecular chain are capped with vinyl groups and has a degree of polymerization of 50 or less, and α,ω-vinyldimethylpolysiloxane is exemplified. This α,ω-vinyldimethylpolysiloxane has the following formula: This is divinyltetramethyldisiloxane. and octamethylcyclotetrasiloxane The degree of polymerization of the polysiloxane intended for is 5 to 50.
It can be obtained by blending as follows, adding an alkali such as caustic potash, or an acid such as sulfuric acid, trifluoromethanesulfonic acid, etc. as a catalyst, and causing an equilibration reaction. The silicone fluid of the present invention is obtained by substituting the terminal vinyl group of this α,ω-vinyldimethylpolysiloxane with a cyclic diorganopolysiloxy group. organopolysiloxane,
For example heptamethylcyclotetrasiloxane is hexamethylcyclotrisiloxane and dichloromethylsilane (CH ₃ ) ₂ SiCl ₂ in equal molar proportions, and hexamethylphosphoamide (HMPA) as a catalyst.

Add [Formula] and stir at room temperature for 2 hours to obtain 1,4-dichloroheptamethyltetrasiloxane. It can be obtained in a yield of 40-50% by synthesizing, hydrolyzing, neutralizing with sodium bicarbonate, and purifying by distillation. The substitution of vinyl groups with this cyclic diorganopolysiloxane is represented by the above formula (3).
A platinum catalyst is added to vinyldimethylpolysiloxane, and heptamethylcyclotetrasiloxane represented by formula (4) is added dropwise at room temperature, and the mixture is stirred and reacted at 110°C. After the reaction is complete, the catalyst is stripped. If the low volatile content is removed using An organopolysiloxane whose molecular chain terminals are blocked with a cyclic dimethylpolysiloxy group is obtained. The silicone fluid of the present invention is mainly composed of an organopolysiloxane obtained by the method described above and whose molecular chain terminals are capped with a cyclic diorganopolysiloxy group. If it is too small, the end of the molecular chain will be blocked with a cyclic diorganopolysiloxy group, resulting in poor fluidity, and if it is over 50, it will have a melting point and crystallization point, so the polymerization degree is 5 to 50. Various organopolysiloxanes are used depending on the types of R ¹ and R ² in the above-mentioned general formula (1), and the following are representative examples. In addition, as mentioned above, the molecular chain terminal is blocked with a cyclic diorganopolysiloxy group, and the degree of polymerization is 5 to 5.
Organopolysiloxane No. 50 has no melting point or crystallization point and exhibits good low-temperature fluidity properties down to the glass transition point, making it useful as a lubricating oil and working oil in cold regions. It can also be used as a base oil for low-temperature grease. Next, examples of the present invention will be given, and parts in the examples indicate parts by weight. Examples 1-3, Comparative Examples 1-2 1,3-divinyltetramethyldisiloxane 1
parts and octamethylcyclotetrasiloxane 20~60
Add 10% potassium siliconate to Si/KOH
= 50,000, and after polymerization (equilibrium reaction) by heating and stirring at 160°C for 8 hours, vinylmethylchlorosilane of 1.5 times the molar amount of KOH and 1,3-divinyltetramethyl of 9 times the weight of this chlorosilane were added. After neutralizing with disilazane and stripping at 180°C, 1.1 times the molar amount of heptamethylcyclotetrasiloxane relative to the vinyl group was added dropwise at room temperature, followed by addition at 110°C using chloroplatinic acid (1 ppm) as a catalyst. After reacting and then stripping it to remove low volatile components, Since the organosiloxane shown by was obtained,
When the physical properties of this were investigated, the results shown in Table 1 below were obtained based on the n value.

[Table] Next, the glass transition temperature, crystallization temperature, and melting point of the silicone oil obtained above were measured using a differential calorimeter and DSC.
(trade name manufactured by Seiko Electronics Co., Ltd.), crystals as shown in Table 2 were obtained, but for comparison, crystals with a degree of polymerization (n) of 50 or more Also listed are the measured values for ordinary dimethylpolysiloxane. In addition, from this result, the silicone oils shown in Examples 1 to 3 whose molecular chain ends were blocked with cyclic diorganopolysiloxy groups and whose polymerization degree was 50 or less had a polymerization degree of 50 or less.
It was confirmed that it has no melting point or crystallization point compared to oils of 50 or higher and dimethylpolysiloxane, and has excellent low-temperature properties.

[Table] In addition, the viscosity-temperature dependence of the silicone oils of Examples 2 and 3 and Comparative Example 2 above was measured using a rheopexi analyzer (manufactured by Iwamoto Seisakusho), and the results are as shown in Table 3. These results confirmed that the silicone oils of Examples 2 and 3 exhibited fluidity up to -100°C.

【table】

Claims (1)

[Claims] 1. General formula [Here, R ¹ is the same or different group selected from an alkyl group having 1 to 8 carbon atoms, a vinyl group, a phenyl group, and a fluoroalkyl group having 3 to 10 carbon atoms,
R ² is the formula (here, Q is a divalent hydrocarbon group having 1 to 6 carbon atoms,
A silicone fluid characterized in that the main material is a diorganopolysiloxane represented by a heteroatom-containing divalent hydrocarbon group, l is an integer of 3 to 6, and n is an integer of 5 to 50. . 2 R ² is the formula The silicone fluid according to claim 1, which is a cyclic dimethylpolysiloxane represented by: 3. The silicone fluid according to claim 1, wherein all R ¹ are methyl groups.