PTC (Positive Temperature Coefficient) heat-conducting gasket for automobile and preparation method thereof

Abstract

The invention discloses a PTC heat-conducting gasket for an automobile and a preparation method thereof. The invention relates to the technical field of heat-conducting materials, in particular to an automobile PTC heat-conducting gasket and a preparation method thereof.The automobile PTC heat-conducting gasket material comprises vinyl silicone oil, end hydrogen-containing silicone oil, side chain hydrogen-containing silicone oil, vinyl silicone resin, heat-conducting filler and a crosslinking catalyst. The silicone oil is especially suitable for heat dissipation and heat management of an automobile PTC heater, solves the problems of poor temperature resistance reliability, large oil penetration rate, poor hardness stability and the like of a thermal interface material caused by low purity of domestic silicone oil, improves the heat conduction performance, mechanical performance and long-term stability of the heat-conducting gasket, and meets the requirement of efficient heat management of the automobile PTC heater.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal conductive materials, and in particular to an automotive PTC thermal conductive gasket and a preparation method thereof, which are particularly suitable for heat dissipation and thermal management of automotive PTC heaters. Background Art

[0002] In the automotive industry, positive temperature coefficient (PTC) heaters are a key heat-generating component, widely used in automotive air conditioning and heating systems. PTC heaters generate significant heat during operation. Failure to effectively and promptly dissipate this heat not only impacts the heater's performance and service life but can also pose safety risks. Therefore, efficient thermal management is crucial for automotive PTC heaters. The performance of thermally conductive gaskets, the thermal interface material connecting the PTC heater to heat dissipation components, directly determines the efficiency and stability of heat transfer.

[0003] At present, silicone thermal interface materials with silicone oil as the skeleton are widely used in the automotive PTC field, but domestic silicone oil has the problem of low purity and high content of small molecule siloxane. This defect leads to many performance problems in silicone thermal interface materials prepared based on domestic silicone oil. First, the heat resistance and reliability are poor. Under high temperature environment, small molecule siloxane is prone to migration, volatilization and other changes, affecting the thermal conductivity and structural stability of the material; second, the oil permeability is high. The leakage of small molecule siloxane will contaminate surrounding components, reduce the fit between the thermal gasket and the PTC heater and heat dissipation components, and thus increase thermal resistance; finally, the hardness stability is poor. The presence of small molecule siloxane and its changes in different environments cause the hardness of the thermal interface material to fluctuate, and stable heat conduction effect and mechanical properties cannot be guaranteed.

[0004] While existing technologies have attempted to address these issues, most have failed to fundamentally overcome the shortcomings of insufficiently pure domestic silicone oils, making it difficult to meet the high-performance and high-reliability requirements of automotive PTC thermal pads. Therefore, there is an urgent need to develop a new automotive PTC thermal pad and its preparation method to improve its overall performance and meet the evolving needs of the automotive industry. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies in the prior art and provide an automotive PTC thermal gasket and a preparation method thereof. Through innovations in raw material component design and process innovations, the present invention solves the problems of poor temperature resistance reliability, high oil permeability, and poor hardness stability of thermal interface materials caused by the low purity of domestic silicone oil, thereby improving the thermal conductivity, mechanical properties, and long-term stability of the thermal gasket and meeting the needs of efficient thermal management of automotive PTC heaters.

[0006] According to its first aspect, the present invention provides a PTC thermally conductive gasket material for automotive use, comprising vinyl silicone oil, end-hydrogenated silicone oil, side-chain hydrogenated silicone oil, vinyl silicone resin, a thermally conductive filler, and a crosslinking catalyst. The end-hydrogenated silicone oil is used to lengthen the molecular chains of the vinyl silicone oil, increasing molecular entanglement. The vinyl silicone resin is grafted onto the main chain of the vinyl silicone oil, and the side-chain hydrogenated silicone oil connects the main chains to form a spatial cage structure.

[0007] In the present invention, vinyl silicone oil is used as a base polymer to provide basic flexibility and processing performance for the thermal conductive gasket; terminal hydrogen-containing silicone oil is used as a chain extender to lengthen the molecular chain of the vinyl silicone oil; side chain hydrogen-containing silicone oil is used as a cross-linking agent to connect the main chain vinyl silicone oils; vinyl silicone resin is used to increase the inorganic structure ratio of the molecular chain; thermal conductive filler is used to improve the thermal conductivity of the gasket; and a cross-linking catalyst promotes the cross-linking reaction.

[0008] Preferably, the automotive PTC thermally conductive gasket material further optionally contains other functional additives. Further preferably, these other functional additives include coupling agents and antioxidants to improve the overall performance of the material. The coupling agent is γ-methacryloxypropyltrimethoxysilane or vinyltrimethoxysilane; the antioxidant is 2,6-di-tert-butyl-p-cresol or Antioxidant 1010.

[0009] Preferably, the vinyl silicone oil includes double-terminal vinyl silicone oil, single-terminal vinyl silicone oil, terminal vinyl silicone oil, and methyl-terminal vinyl silicone oil. In one embodiment, the viscosity of the vinyl silicone oil is 500 mPa·s.

[0010] Preferably, the hydrogen-terminated silicone oil includes double-terminated hydrogen-terminated silicone oil and single-terminated hydrogen-terminated silicone oil; in one embodiment, the hydrogen content of the hydrogen-terminated silicone oil is 0.15%.

[0011] Preferably, the side chain hydrogen-containing silicone oil includes methyl side hydrogen silicone oil and terminal side hydrogen-containing silicone oil; in one embodiment, the hydrogen content of the side chain hydrogen-containing silicone oil is 0.08%.

[0012] Preferably, the vinyl silicone resin includes MQ-type vinyl silicone resin, phenyl-vinyl silicone resin, and hydrogenated vinyl silicone resin.

[0013] Preferably, the thermally conductive filler includes any one or more of alumina powder and aluminum nitride powder.

[0014] Preferably, the cross-linking catalyst includes any one of chloroplatinic acid-isopropanol solution or chloroplatinic acid-tetrahydrofuran solution.

[0015] Preferably, the mass ratio of the hydrogen-terminated silicone oil to the vinyl silicone oil is (3-10):100; more preferably (7-8):100.

[0016] Preferably, the mass ratio of the side chain hydrogenated silicone oil to the vinyl silicone oil is (3-8):100; more preferably (5-6):100.

[0017] Preferably, the mass ratio of the vinyl silicone resin to the vinyl silicone oil is (5-20):100; more preferably (10-15):100.

[0018] Preferably, the mass ratio of the thermal conductive filler to the vinyl silicone oil is (1700-2500):100; more preferably (1950-2200):100.

[0019] Preferably, the mass ratio of the cross-linking catalyst to the vinyl silicone oil is (0.1-0.9):100; more preferably (0.3-0.6):100.

[0020] Preferably, when a coupling agent is present, the mass ratio of the coupling agent to the vinyl silicone oil is (1-5):100; more preferably (2-3):100; and / or, when an antioxidant is present, the mass ratio of the antioxidant to the vinyl silicone oil is (0.5-2.0):100; more preferably (1-1.5):100.

[0021] According to a second aspect of the present invention, the present invention provides a method for preparing the automotive PTC thermally conductive gasket, comprising the following steps: Mixing: Vinyl silicone oil, terminal hydrogen silicone oil, side chain hydrogen silicone oil, vinyl silicone resin, thermal conductive filler, coupling agent and antioxidant are mixed evenly; Cross-linking reaction: adding a cross-linking catalyst to initiate the cross-linking reaction; Molding: The mixed material is injected into the mold and solidified into shape.

[0022] Preferably, the vinyl silicone oil is pre-treated by vacuum heating before mixing: the vinyl silicone oil is vacuum heated to remove small molecular siloxanes. Further preferred conditions for the vacuum heating treatment are a vacuum degree of -0.09 MPa to -0.095 MPa, a temperature of 120°C to 130°C, and a treatment time of 2.5 to 3 hours.

[0023] Preferably, in the mixing step, the mixture is stirred at 30-50° C. for 1-5 hours.

[0024] Preferably, in the cross-linking reaction step, stirring is continued for 20-60 minutes after the cross-linking catalyst is added.

[0025] Preferably, in the molding step, curing is performed at 100-150° C. (eg, 130° C.) for 1-5 hours (eg, 2 hours).

[0026] Technical principle of the present invention: 1. Ingredient Design Innovation Optimization of the molecular chain structure based on vinyl silicone oil: Based on the molecular chain structure of vinyl silicone oil, end-hydrogen silicone oil is used as a chain extender to lengthen the molecular chain. During the reaction process, the hydrogen atoms in the end-hydrogen silicone oil undergo a silylation reaction with the vinyl groups at both ends of the vinyl silicone oil molecular chain, thereby extending the molecular chain. The lengthening of the molecular chain increases the entanglement of the molecules. On the one hand, it can wrap the powder to a greater extent, increase the upper limit of the powder particle size, and allow more thermally conductive fillers to be evenly dispersed in the system, which is beneficial to improving the thermal conductivity of the gasket; on the other hand, it increases the flexibility of the molecular chain, improves the flexibility of the interface material, reduces the interface thermal resistance, and allows heat to be transferred more smoothly through the thermally conductive gasket.

[0027] Increase the inorganic structure ratio of the molecular chain: Graft a spatial network of vinyl silicone resin onto the main chain of vinyl silicone oil. Through precise calculation, the inorganic structure of the vinyl silicone resin is evenly dispersed at different positions of the main chain. Then, using side chain hydrogen silicone oil as a crosslinking agent, under the action of a crosslinking catalyst, a crosslinking reaction occurs between the main chains, forming a spatial cage structure similar to the uniform distribution of islands. This structure has multiple advantages: first, it increases the internal strength and flexibility of the molecular chain, thereby improving the bending strength of the interface material, so that the thermal gasket can better resist external force deformation in the complex use environment of the car and maintain structural integrity; second, the inorganic structure of the vinyl silicone resin can increase the wettability of the molecular chain and the substrate (such as PTC heaters and heat dissipation components), as well as the gripping force on the substrate, reducing the interfacial thermal resistance and ensuring good heat conduction effect; third, the formed mesh cage-type space structure can effectively lock small molecule siloxanes, minimize their precipitation, and reduce oil seepage rate; fourth, the inorganic structure itself has a certain thermal conductivity, which can increase the overall thermal conductivity of the interface material; fifth, the inorganic structure also improves the insulation pressure resistance of the material, meeting the insulation performance requirements of the automotive electrical system.

[0028] 2. Process Innovation A specific vacuum heating process is used to pre-treat the vinyl silicone oil. The vinyl silicone oil is placed in a vacuum environment and heated at a certain temperature. Under vacuum conditions, the boiling point of small molecule siloxanes decreases, making it easier for them to volatilize and escape from the system. By controlling the heating temperature and time, the small molecule siloxanes in the vinyl silicone oil can be effectively removed. This process innovation has the following effects: on the one hand, it reduces the possibility of small molecule precipitation and seepage, solving the oil leakage problem caused by small molecule siloxanes at the source; on the other hand, it reduces the proportion of small molecule silane repolymerization, so that the overall vinyl content reaches a relatively stable threshold, thereby stabilizing the hardness of the interface material and ensuring the consistency of the performance of the thermal pad under different usage conditions.

[0029] Compared with the prior art, the present invention has the following beneficial effects: 1. Excellent thermal conductivity: By optimizing the molecular chain structure and increasing the proportion of inorganic structure, the interfacial thermal resistance is reduced, while the upper limit of the addition amount of thermal conductive filler is increased, and the overall thermal conductivity of the material is improved. It can quickly and effectively transfer the heat generated by the PTC heater, meeting the needs of efficient heat dissipation of automotive PTC heaters.

[0030] 2. Good mechanical properties: The improvement of the molecular chain structure and the formation of a spatial cage structure increase the internal strength and flexibility of the material, improve the bending strength and deformation resistance of the thermal pad, and enable it to maintain structural integrity and stability in complex vibration, impact and other environments of the car.

[0031] 3. Low oil permeability and stable hardness: By removing small molecular siloxanes from vinyl silicone oil and forming a spatial structure that locks the small molecules, the oil permeability is significantly reduced, reducing pollution to surrounding components; at the same time, the vinyl content is stabilized, ensuring the stability of the hardness, and improving the long-term reliability and service life of the thermal pad.

[0032] 4. High insulation voltage resistance: The introduction of inorganic structure improves the insulation voltage resistance of the material, meets the strict requirements of the automotive electrical system on insulation performance, and enhances the safety of automobile use. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a schematic diagram of the molecular structure of the automotive PTC thermal pad of the present invention, showing the spatial cage structure formed by the interaction of vinyl silicone oil, vinyl silicone resin, terminal hydrogen silicone oil and side chain hydrogen silicone oil; Figure 2 This is a process flow chart for the preparation of automotive PTC thermal pads, detailing each step from raw material pretreatment to finished product preparation.

[0034] Figure 3 This is a picture of the product prepared in Example 1 after being bent 180°.

[0035] Figure 4 This is a picture of the product prepared in Example 2 after being bent 180°.

[0036] Figure 5 The following is a picture of a product prepared for comparison after being bent 180°. DETAILED DESCRIPTION

[0037] Example 1: 1. Raw Materials Preparation (Calculated by weight, the rest are the same; unless otherwise specified in this invention, the content is by weight) Vinyl silicone oil: 100 parts of Runhe Material's RH-Vi311 vinyl silicone oil with a viscosity of 500mPa·s; End-hydrogenated silicone oil: 7.7 parts of Runhe Material's RH-H45 end-hydrogenated silicone oil with a hydrogen content of 0.12%; Side chain hydrogen silicone oil: 5.5 parts of Runhe Material's RH-H33 side chain hydrogen silicone oil with a hydrogen content of 0.18%; Vinyl silicone resin: 12 parts of CX-3612MQ vinyl silicone resin from Chensi New Materials; Thermal conductive filler: 2000 parts of SLA-20 alumina powder (average particle size 20μm) from Yishitong Materials; Cross-linking catalyst: 0.5 parts of chloroplatinic acid-isopropyl alcohol solution (platinum content 0.5%) from Siyou New Materials; Coupling agent: 2 parts of γ-methacryloxypropyltrimethoxysilane from Jiahua Silicone; Antioxidant: 1 part of 2,6-di-tert-butyl-4-cresol from Haishan Technology.

[0038] 2. Preparation process unit operation Vinyl silicone oil pretreatment: Vinyl silicone oil was placed in a vacuum drying oven and heated at a vacuum degree of -0.09 MPa and a temperature of 120° C. for 3 hours to remove the small molecular siloxane therein.

[0039] mix The pretreated vinyl silicone oil, terminal hydrogen silicone oil, side chain hydrogen silicone oil, vinyl silicone resin, thermal conductive filler, coupling agent and antioxidant were added to a planetary mixer and stirred and mixed at 40° C. for 3 hours to ensure that the components were fully dispersed.

[0040] Addition reaction Then, a cross-linking catalyst was added and stirring was continued for 30 minutes to initiate the cross-linking reaction.

[0041] forming The uniformly mixed material is rolled into sheets, and then cured at 130° C. for 2 hours to obtain an automotive PTC thermal conductive gasket.

[0042] Example 2: 1. Raw material preparation Vinyl silicone oil: 100 parts of Runhe Material's RH-Vi305 vinyl silicone oil with a viscosity of 1000 mPa·s; End-hydrogenated silicone oil: 8 parts of Runhe Material's RH-H6 end-hydrogenated silicone oil with a hydrogen content of 0.12%; Side chain hydrogen silicone oil: 6 parts of Runhe Material's RH-H35 side chain hydrogen silicone oil with a hydrogen content of 0.12%; CX-3612MQ vinyl silicone resin from Chensi New Materials: 14 parts; Thermal conductive filler: 2100 parts of SLA-45 powder from Yishitong Materials; Cross-linking catalyst: 0.6 parts of chloroplatinic acid-tetrahydrofuran solution (platinum content 0.3%) from Siyou New Materials; Coupling agent: 3 parts of vinyltrimethoxysilane from Jiahua Silicone; Antioxidant: 1.5 parts of Haishan Technology's antioxidant 1010.

[0043] 2. Preparation process unit operation Vinyl silicone oil pretreatment The vinyl silicone oil was vacuum-heated at a temperature of 120° C. for 3 hours at a vacuum degree of −0.09 MPa.

[0044] The subsequent steps are the same as those in Example 1, and finally a PTC thermal conductive gasket for automobiles is obtained.

[0045] Comparative Example (conventional prior art solution): 1. Raw material preparation Vinyl silicone oil: 100 parts of Runhe Material's RH-Vi305 vinyl silicone oil with a viscosity of 1000 mPa·s; End-hydrogenated silicone oil: 14 parts of Runhe Material's RH-H6 end-hydrogenated silicone oil with a hydrogen content of 0.12%; Thermal conductive filler: 2100 parts of SLA-45 powder from Yishitong Materials; Cross-linking catalyst: 0.6 parts of chloroplatinic acid-tetrahydrofuran solution (platinum content 0.3%) from Siyou New Materials; Coupling agent: 3 parts of vinyltrimethoxysilane from Jiahua Silicone; Antioxidant: Use 1.5 parts of Haishan Technology's antioxidant 1010.

[0046] 2. Preparation process unit operation The vinyl silicone oil was not pretreated, and the subsequent steps were the same as in Example 1 to finally obtain an automotive PTC thermally conductive gasket.

[0047] The performance tests of the automotive PTC thermally conductive gaskets prepared in Example 1, Example 2 and the comparative example were conducted, and the results were as follows: It can be seen from the performance test data that the automotive PTC thermal gasket prepared by the present invention has excellent thermal conductivity, low oil permeability, stable hardness, good mechanical properties and insulation withstand voltage performance, and can meet the application requirements in the automotive PTC field.

[0048] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A PTC thermal conductive gasket material for automobiles, comprising vinyl silicone oil, terminal hydrogen silicone oil, side chain hydrogen silicone oil, vinyl silicone resin, thermal conductive filler, and a cross-linking catalyst. 2 . The automotive PTC thermally conductive gasket material according to claim 1 , wherein the automotive PTC thermally conductive gasket material optionally comprises a coupling agent and an antioxidant functional additive.

3. The automotive PTC thermal conductive gasket material according to claim 2, The thermally conductive filler includes aluminum oxide powder and aluminum nitride powder; And / or, the cross-linking catalyst comprises chloroplatinic acid-isopropanol solution or chloroplatinic acid-tetrahydrofuran solution; and / or, the coupling agent is γ-methacryloxypropyltrimethoxysilane or vinyltrimethoxysilane; And / or, the antioxidant is 2,6-di-tert-butyl-p-cresol or antioxidant 1010; And / or, the vinyl silicone oil includes double-terminal vinyl silicone oil, single-terminal vinyl silicone oil, terminal vinyl silicone oil or methyl-terminal vinyl silicone oil; And / or, the hydrogen-terminated silicone oil includes double-terminated hydrogen-terminated silicone oil and single-terminated hydrogen-terminated silicone oil; And / or, the side chain hydrogen-containing silicone oil includes methyl side hydrogen silicone oil and terminal side hydrogen-containing silicone oil; And / or, the vinyl silicone resin includes MQ-type vinyl silicone resin, phenyl-vinyl silicone resin, and hydrogenated vinyl silicone resin.

4. The automotive PTC thermal conductive gasket material according to claim 3, wherein the mass ratio of the hydrogenated silicone oil to the vinyl silicone oil is (3-10):100; And / or, the mass ratio of the side chain hydrogen silicone oil to the vinyl silicone oil is (3-8):100; and / or, the mass ratio of the vinyl silicone resin to the vinyl silicone oil is (5 - 20):100; And / or, the mass ratio of the thermal conductive filler to the vinyl silicone oil is (1700 - 2500):100; and / or, the mass ratio of the cross-linking catalyst to the vinyl silicone oil is (0.1 - 0.9):100; and / or, the mass ratio of the coupling agent to the vinyl silicone oil is (1-5):100; And / or, the mass ratio of the antioxidant to the vinyl silicone oil is (0.5-2.0):

100.

5. A method for preparing the automotive PTC thermally conductive gasket material according to any one of claims 1 to 4, comprising the following steps: Mixing: Vinyl silicone oil, terminal hydrogen silicone oil, side chain hydrogen silicone oil, vinyl silicone resin, thermal conductive filler, coupling agent and antioxidant are mixed evenly; Cross-linking reaction: adding a cross-linking catalyst to initiate the cross-linking reaction; Molding: The mixed material is injected into the mold and solidified into shape.

6. The method according to claim 5, wherein the vinyl silicone oil is pretreated by vacuum heating before mixing.

7. The method according to claim 6, wherein the vacuum heat treatment conditions are: vacuum degree -0.09 MPa to -0.095 MPa, temperature 120°C to 130°C, and treatment time 2.5 hours to 3 hours.

8. The method according to claim 5, In the mixing step, stirring and mixing at 30-50° C. for 1-5 hours; and / or, in the cross-linking reaction step, stirring is continued for 20-60 minutes after adding the cross-linking catalyst; And / or, in the molding step, curing is performed at 100-150° C. for 1-5 hours.

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