PPTC polymer composition

Abstract

This application relates to the field of polypropylene thermocouple (PPTC) technology, specifically providing a PPTC polymer composition. The PPTC polymer composition comprises, by weight, 100 parts of a base polymer and 20-60 parts of a polyurethane-grafted conductive filler; the polyurethane of the polyurethane-grafted conductive filler contains at least a first segment formed from a long-chain alkyl glycol and / or a fluoroalkyl glycol. The PPTC polymer composition, used in PPTC, exhibits low normal operating resistance, rapid resistance recovery after a trip, and a high operating current.

Description

Technical Field

[0001] The present application relates to the field of PPTC technology, and in particular, to a PPTC polymer composition. Background Art

[0002] Polymer positive temperature coefficient (PPTC) devices can be used in overcurrent or overtemperature protection devices, as well as current or temperature sensors. PPTCs provide circuit protection by switching from a low resistance to a high resistance at a certain temperature or within a narrow temperature range (also known as the trip temperature) when exposed to overcurrent or overheating. This change in resistance gives PPTCs a fuse-like effect. When the PPTC cools to room temperature, its resistance returns to its low state, providing good conductivity. Therefore, the resistance change in PPTCs is reversible.

[0003] After the PPTC trips, the conductive path of the conductive filler needs to be gradually restored. Therefore, the recovery rate of the conductive path (usually marked as R 1max , that is, the resistance after the jump to restore 1 hour) is one of the important performance parameters of PPTC. 1max The performance is not good enough. Summary of the Invention

[0004] To address the above-mentioned issues, the inventors, after extensive research and analysis, discovered that the cause of these technical problems is that, after a period of use, the bonding strength between the conductive fillers dispersed within the PPTC polymer material and the matrix polymer deteriorates. Based on this, the inventors conducted extensive research, testing, and analysis. Therefore, the present application is filed.

[0005] The present application provides a PPTC polymer composition.

[0006] This application adopts the following technical solutions:

[0007] The PPTC polymer composition comprises, by weight, 100 parts of a base polymer and 20-60 parts of a polyurethane graft-modified conductive filler;

[0008] The polyurethane of the polyurethane graft-modified conductive filler contains at least a first segment formed by long-chain alkyl glycol and / or fluoroalkyl glycol.

[0009] Preferably, the general formula of the long-chain alkyl glycol is HOR 1 OH, where R 1 Selected from C10-C40 alkylene groups.

[0010] Preferably, the general formula of the fluoroalkyl diol is HOR 2 OH, where R2 is selected from C6-C20 fluorinated alkylene groups, and R 2 The proportion of carbon atoms directly connected to fluorine in the total carbon atoms is not less than 40%.

[0011] Preferably, the preparation method of the polyurethane grafted modified conductive filler comprises the following steps:

[0012] S1. The long-chain alkyl diol and / or the fluoroalkyl diol reacts with polyisocyanate to obtain an isocyanate-terminated prepolymer; S2. The conductive filler is dispersed in an organic solvent to prepare a dispersion, and the isocyanate-terminated prepolymer described in step S1 is added thereto, reacted, filtered, washed, and dried to obtain the product.

[0013] More preferably, amino groups are grafted onto the surface of the conductive filler in step S2.

[0014] More preferably, in step S2, the weight ratio of the conductive filler, the organic solvent, and the isocyanate-terminated prepolymer is 1:10-1000:0.01-0.5.

[0015] Preferably, the polyurethane of the polyurethane grafted modified conductive filler further contains a second segment formed by polyester polyol and / or polyether polyol, the first segment and the second segment are arranged alternately, and adjacent first segment and second segment are connected by a carbamate bond.

[0016] Preferably, the polymer matrix is ​​selected from one of polyolefins, fluorinated polyolefins and derivatives thereof.

[0017] Preferably, the raw material components further contain 0.5-5 parts of auxiliary agents.

[0018] More preferably, the auxiliary agent is selected from at least one of an antioxidant, a stabilizer and a lubricant.

[0019] In summary, this application has at least the following beneficial effects:

[0020] 1. To improve the dispersibility and bonding between the conductive filler and the matrix polymer, this application uses polyurethane as a surface treatment agent for the conductive filler. Polyurethane has good compatibility with the matrix polymer and, at room temperature, exhibits physical crosslinking between hard and soft segments and polymer chains. When the temperature rises, such as near the transition temperature, the physical crosslinking between the polyurethane polymer chains weakens or disappears, and the polymer chains become softer, which does not affect the expansion of the matrix polymer or the transition from connection to separation of the conductive filler. When the temperature returns to room temperature or the normal operating temperature of the PPTC, the hard and soft segments of the polyurethane polymer chains and the physical crosslinking between the polymer chains are restored, resuming the compatibility between the conductive filler and the polymer matrix, and the PPTC returns to a low-resistance state.

[0021] 2. The base polymer of PPTC is generally polyolefin or fluorine-containing polymer. This application introduces long-chain alkyl and / or fluoroalkyl groups into the polyurethane structure, and the corresponding polyurethane has good compatibility with the base polymer. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described in detail below.

[0023] Throughout this specification, unless otherwise specified, the terms used herein should be understood as having the same meaning as commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In the event of any conflict, the present specification shall take precedence.

[0024] The present application proposes a PPTC polymer composition, wherein the raw material components, calculated by weight, include: 100 parts of a base polymer and 20-60 parts of a polyurethane graft-modified conductive filler;

[0025] The polyurethane of the polyurethane graft-modified conductive filler contains at least a first segment formed of a long-chain alkyl glycol and / or a fluoroalkyl glycol.

[0026] The matrix composition in PPTC generally uses polyolefins or fluorinated polyolefins and their derivatives. This application uses polyurethane as a surface modifier for the conductive filler. The polyurethane structure contains long-chain alkyl and / or fluoroalkyl groups, which improves compatibility with polyolefins or fluorinated polyolefins, making the conductive filler and the matrix polymer compatible. Moreover, the polyurethane structure contains soft and hard segment structures and physical crosslinking structures. When the temperature rises, such as at a certain temperature, below or close to the trip temperature of PPTC, the physical crosslinking structure in the polyurethane segment basically disappears, and the soft and hard segment structures are also not obvious. At this time, it does not affect the expansion of the matrix polymer and the disconnection of the conductive filler. When the PPTC returns to room temperature or normal operating temperature, the soft and hard segment structures and physical crosslinking structures in the polyurethane segment recover, and the compatibility between the conductive filler and the matrix polymer is re-established. Therefore, this application utilizes the above-mentioned properties of polyurethane to maintain good compatibility and bonding between the conductive filler and the matrix polymer during the use period of PPTC, and after the trip temperature occurs, the resistance can recover faster.

[0027] In this application, there is no particular limitation on the conductive filler, and the shape can be granular, needle-shaped, fibrous, lamellar, etc., and the material can be carbon material, metal material, ceramic metal material, etc., such as carbon fiber, carbon fiber, carbon black, graphite, copper, silver, aluminum, etc. The average particle size of the conductive filler can range from 50 nm to 100 μm.

[0028] In a preferred embodiment of the present application, the general formula of the long-chain alkyl glycol is HOR1 OH, where R 1 is selected from C10-C40 alkylene. More preferably, R 1 is selected from C10-C40 straight chain alkylene. 1 The long-chain alkylene group may be selected from C10-C40 alkylene groups or linear alkylene groups, which can provide good compatibility between the polyurethane segments and the polyolefin as the matrix polymer. For example, the long-chain alkyl glycol may be 1,10-decanediol, 1,12-dodecanediol, 1,18-octadecanediol, 1,22-behenanediol, etc.

[0029] In a preferred embodiment of the present application, the general formula of fluoroalkyl diol is HOR 2 OH, where R 2 is selected from C6-C20 fluorinated alkylene groups, and R 2 The proportion of carbon atoms directly connected to fluorine in the total carbon atoms is not less than 40%. 2 The fluorinated alkylene group selected from C6-C20 can provide good compatibility between the polyurethane segment and the fluorinated polyolefin and its derivatives as the matrix polymer. 2 It can be the following structure -(CH2) m (CF2) n (CH2) m -, where 6≤n+2m≤20, n / (n+2m)≥0.4, for example, -(CH2)2(CF2)4(CH2)2-, -(CH2)2(CF2)6(CH2)2-, -(CH2)2(CF2)8(CH2)2-, -(CH2)2(CF2) 10 (CH2)2-, etc.

[0030] In a preferred embodiment of the present application, the preparation method of the polyurethane grafted modified conductive filler comprises the following steps:

[0031] S1. reacting a long-chain alkyl glycol and / or a fluoroalkyl glycol with a polyisocyanate to obtain an isocyanate-terminated prepolymer;

[0032] S2. The conductive filler is dispersed in an organic solvent to prepare a dispersion, and the isocyanate-terminated prepolymer of step S1 is added thereto, reacted, filtered, washed, and dried to obtain the product.

[0033] In the above preparation method, the molar ratio of the long-chain alkyl diol and / or fluoroalkyl diol to the polycyanate can be 0.7-0.93: 1. The polyisocyanate can be a diisocyanate, such as IPDI, HMDI, TDI, HDI, etc.

[0034] In the above step S2, the organic solvent is an aprotic organic solvent, such as acetone, methyl ethyl ketone, tetrahydrofuran, 1,4-dioxane, ethyl acetate, butyl acetate, etc.

[0035] In a more preferred embodiment of the present application, amino groups, such as primary amino groups, are grafted onto the surface of the conductive filler in step S2. After the amino groups are grafted onto the surface of the conductive filler, the reactivity with the isocyanate prepolymer is higher, and the isocyanate prepolymer can be grafted onto the surface of the conductive filler more quickly and completely to obtain a polyurethane grafted modified conductive filler. Specifically, there is no particular limitation on the method for grafting amino groups onto the surface of the conductive filler. For example, an amino-containing silane coupling agent can be used, for example, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-aminoethyl-N-aminopropyltrimethoxysilane, N-aminoethyl-N-aminopropyltriethoxysilane, etc. For example, a method for preparing a carbon black surface grafted with amino groups is as follows: 3 parts by weight of 3-aminopropyltrimethoxysilane are added to 97 parts by weight of an alcohol-water solution composed of anhydrous ethanol and water in a volume ratio of 9:1, stirred for 1 hour for hydrolysis, 20 parts by weight of carbon black particles are added, stirred for reaction for 3 hours, the solid is collected by filtration, washed twice with anhydrous ethanol, and dried in an oven at 60°C overnight.

[0036] In the above-mentioned preparation method of the polyurethane graft-modified conductive filler, after the isocyanate-terminated prepolymer is added for reaction in step S2, methanol or ethanol can be further added to react with the unreacted terminal isocyanate groups to cap the isocyanate groups and improve the stability of the polyurethane graft-modified conductive filler.

[0037] In a preferred embodiment of the present application, the weight ratio of the conductive filler, the organic solvent, and the isocyanate-terminated prepolymer in step S2 is 1:10-1000:0.01-0.5. More preferably, the weight ratio of the conductive filler, the organic solvent, and the isocyanate-terminated prepolymer is 1:10-500:0.1-0.4.

[0038] In a preferred embodiment of the present application, the polyurethane grafted modified conductive filler further comprises a second segment formed from a polyester polyol and / or a polyether polyol, wherein the first and second segments are arranged alternately, and adjacent first and second segments are connected by a urethane bond. The introduction of polyester or polyether into the polyurethane structure can serve as a soft segment structure. Polyether can improve the soft segment's flexibility, while polyester can improve the polyurethane structure's heat resistance. For example, the molar ratio of long-chain alkyl glycol and / or fluoroalkyl glycol to polyester polyol and / or polyether polyol can be 1:0.05-0.2.

[0039] In a preferred embodiment of the present application, the polymer matrix is ​​selected from a polyolefin and a fluorinated polyolefin and its derivatives. For example, the polyolefin may be polyethylene, such as low-density polyethylene (LDPE), high-density polyethylene (HDPE), medium-density polyethylene (MDPE), etc.; the fluorinated polyolefin and its derivatives may be ethylene tetrafluoroethylene copolymer (ETFE), polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTEF), polyperfluoroalkoxy (PFAS), polytetrafluoroethylene perfluoropropylene (PTFE), polyvinylidene fluoride (PVDF), or other fluoropolymers.

[0040] In a preferred embodiment of the present application, the raw material components may further include 0.5-5 parts of an additive, depending on processing and usage requirements. The additive may be selected from at least one of an antioxidant, a stabilizer, and a lubricant, such as 0.5-1 parts of an antioxidant, 0.6-2 parts of a stabilizer, and 0.8-2 parts of a lubricant. Antioxidants, stabilizers, and lubricants can all be obtained directly from commercially available products, with stabilizers being more commonly used in PVC polymers.

[0041] The PPTC polymer composition of the present application can be prepared by the following method: after drying and removing water from each raw material component, add it into a mixer and stir it evenly, then transfer it into a screw extruder for extrusion, calendaring, and molding.

[0042] The technical solution of the present application is described in detail below with reference to the following examples and comparative examples. Unless otherwise specified, the parts in the following preparation examples, examples and comparative examples are parts by weight.

[0043] Preparation Example 1-4 Preparation of polyurethane grafted modified conductive filler

[0044] Preparation Example 1

[0045] 1,12-Dodecyl glycol and IPDI were added to a container in a molar ratio of 0.9:1, stirred at room temperature for 2 hours, heated to 70°C and stirred for 2 hours to obtain an isocyanate-terminated prepolymer;

[0046] 10 parts of amino-modified carbon black (average particle size 2 μm) were dispersed in 200 parts of butyl acetate to prepare a dispersion, 3 parts of the above-mentioned isocyanate-terminated prepolymer were added, and the mixture was stirred and reacted for 2 hours. Then 1 part of methanol was added and the mixture was stirred and reacted for another 2 hours. The mixture was filtered, and the solid was washed twice with anhydrous ethanol and dried in an oven at 60°C overnight to obtain polyurethane-grafted modified carbon black.

[0047] Preparation Example 2

[0048] The difference between Preparation Example 2 and Preparation Example 1 is that the 1,12-dodecanediol in Preparation Example 1 is replaced with an equal molar amount of 1,22-docosandiol. The remaining steps remain unchanged.

[0049] Preparation Example 3

[0050] 1,12-Dodecyl glycol, polypropylene glycol (average molecular weight 600) and IPDI were added to a container in a molar ratio of 0.82:0.08:1, stirred at room temperature for 2 hours, heated to 70°C and stirred for 2 hours to obtain an isocyanate-terminated prepolymer; 10 parts of the amino-modified carbon black in Preparation Example 1 were dispersed in 200 parts of butyl acetate to prepare a dispersion, 3 parts of the above-mentioned isocyanate-terminated prepolymer were added, stirred and reacted for 2 hours, and then 1 part of methanol was added, and the stirring reaction was continued for 2 hours. The mixture was filtered, and the solid was washed twice with anhydrous ethanol and dried in an oven at 60°C overnight to obtain a polyurethane-grafted modified carbon black.

[0051] Preparation Example 4

[0052] Fluoroalkyl diol HO(CH2)2(CF2)8(CH2)2OH and IPDI were added into a container in a molar ratio of 0.85:1, stirred at room temperature for 2 hours, heated to 70°C and stirred for 3 hours to obtain an isocyanate-terminated prepolymer;

[0053] 10 parts of amino-modified carbon black (average particle size 1 μm) were dispersed in 300 parts of butyl acetate to prepare a dispersion, 4 parts of the above-mentioned isocyanate-terminated prepolymer were added, and the mixture was stirred and reacted for 2 hours. Then 1 part of ethanol was added, and the mixture was stirred and reacted for 2 hours. The mixture was filtered, and the solid was washed twice with anhydrous ethanol and dried in an oven at 60°C overnight to obtain polyurethane-grafted modified carbon black.

[0054] Example 1

[0055] The PPTC polymer composition consists of 100 parts of HDPE, 20 parts of the polyurethane graft-modified carbon black of Preparation Example 1, and 0.8 parts of antioxidant 168.

[0056] After drying and removing water from the raw material components, add them to the mixer and mix them evenly. Then transfer them to the twin-screw extruder for melting, extrusion, calendering, and molding to make a 0.5mm thick sheet. The temperature settings of the twin-screw extruder are: zone 1 temperature 120-130℃, zone 2 temperature 150-160℃, zone 3 temperature 180-190℃, zone 4 temperature 220-230℃, zone 5 temperature 220-230℃, zone 6 temperature 220-230℃, zone 7 temperature 220-230℃, zone 8 temperature 200-210℃, zone 9 temperature 190-200℃, and die head temperature 190℃.

[0057] Example 2

[0058] The difference between Example 2 and Example 1 is that the polyurethane graft-modified carbon black in Preparation Example 1 is adjusted from 20 parts to 40 parts. The other steps remain unchanged.

[0059] Example 3

[0060] The difference between Example 3 and Example 1 is that the polyurethane graft-modified carbon black in Preparation Example 1 is adjusted from 20 parts to 60 parts. The other steps remain unchanged.

[0061] Example 4

[0062] The difference between Example 4 and Example 2 is that the polyurethane grafted modified carbon black of Preparation Example 1 is replaced by an equal weight portion of the polyurethane grafted modified carbon black of Preparation Example 2. The remaining steps remain unchanged.

[0063] Example 5

[0064] The difference between Example 5 and Example 2 is that the polyurethane grafted modified carbon black of Preparation Example 1 is replaced by an equal weight portion of the polyurethane grafted modified carbon black of Preparation Example 3. The remaining steps remain unchanged.

[0065] Comparative Example 1

[0066] The difference between Comparative Example 1 and Example 2 is that the polyurethane grafted modified carbon black in Example 2 is replaced by an equal weight portion of the amino modified carbon black in Preparation Example 1. The remaining steps remain unchanged.

[0067] Comparative Example 2

[0068] The difference between Comparative Example 2 and Example 2 is that the polyurethane grafted modified carbon black in Example 2 is replaced by an equal weight portion of the carbon black before modification in Preparation Example 1. The remaining steps remain unchanged.

[0069] Comparative Example 3

[0070] The difference between Comparative Example 3 and Example 2 is that the polyurethane grafted modified carbon black in Example 2 is replaced by an equal weight portion of dodecyl modified carbon black. The remaining steps remain unchanged.

[0071] The preparation method of dodecyl-modified carbon black is as follows: add 2 parts of n-dodecyltrimethoxysilane to 98 parts of an alcohol-water solution composed of anhydrous ethanol and water in a volume ratio of 9:1, add acid to adjust the pH to 3-3.5, stir for 1 hour for hydrolysis, add 20 parts of the carbon black particles before modification in Preparation Example 1, stir and react for 3 hours, filter and collect the solid, wash twice with anhydrous ethanol, and dry in an oven at 60°C overnight to obtain the product.

[0072] Comparative Example 4

[0073] The PPTC polymer composition is composed of 100 parts of HDPE, 36 parts of amino-modified carbon black in Preparation Example 1, and 4 parts of isocyanate-terminated prepolymer in Preparation Example 1. The molding method of Example 1 is used for processing.

[0074] Example 6

[0075] The PPTC polymer composition consists of 100 parts of ETFE, 30 parts of the polyurethane graft-modified carbon black of Preparation Example 4, and 0.8 parts of antioxidant 168.

[0076] After drying and removing water from the raw material components, add them to the mixer and mix them evenly. Then transfer them to the twin-screw extruder for melting, extrusion, calendaring, and molding to make a 0.4mm thick sheet. The temperature settings of the twin-screw extruder are: zone 1 temperature 180-190℃, zone 2 temperature 220-230℃, zone 3 temperature 260-270℃, zone 4 temperature 300-310℃, zone 5 temperature 310-320℃, zone 6 temperature 310-320℃, zone 7 temperature 310-320℃, zone 8 temperature 300-310℃, zone 9 temperature 300-310℃, and die head temperature 300℃.

[0077] Example 7

[0078] The difference between Example 7 and Example 6 is that the polyurethane graft-modified carbon black in Preparation Example 4 is adjusted from 30 parts to 45 parts. The other steps remain unchanged.

[0079] Comparative Example 5

[0080] The difference between Comparative Example 5 and Example 6 is that the polyurethane grafted modified carbon black in Preparation Example 4 is replaced by an equal weight portion of the unmodified carbon black in Preparation Example 4, and 5 parts of dispersant Efka PX 4787 are added. The remaining steps remain unchanged.

[0081] Performance Testing

[0082] The top and bottom layers of the PPTC polymer sheet to be tested are laminated onto a PCB. The PCB is gold-plated and cut to the desired size, with SMD pins reserved at both ends. The test is performed using an electrical performance tester.

[0083] R0: Resistance under normal operation before jumping.

[0084] R 1max : Maximum resistance value after 1 hour recovery at room temperature after the trip operation.

[0085] I trip : Action current. When the current is greater than this current, the impedance will become extremely large in a very short period of time and the circuit will be interrupted.

[0086] T trip : Action time, the time when the PPTC impedance changes from small to large under the above action current.

[0087] The results are shown in Table 1 below.

[0088] Table 1

[0089]

[0090]

[0091] As can be seen from the data results in Table 1 above, the PPTC polymer composition of the present application has the characteristics of low normal operating resistance and fast resistance recovery after tripping, and the operating current is relatively high. This shows that the combination of the matrix polymer and the conductive filler inside the PPTC polymer composition of the present application is more stable, and it can recover faster after a circuit breaker occurs.

[0092] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. PPTC polymer composition, characterized in that The raw material components, calculated by weight, include: 100 parts of a base polymer and 40-60 parts of a polyurethane graft-modified conductive filler, wherein the base polymer is selected from one of polyolefin and fluorinated polyolefin, and the conductive filler is carbon black with amino groups grafted on the surface; The polyurethane of the polyurethane graft-modified conductive filler contains at least a first segment formed by a long-chain alkyl glycol and / or a fluoroalkyl glycol; The general formula of the long chain alkyl glycol is HOR 1 OH, where R 1 Selected from C10-C40 alkylene; The general formula of the fluoroalkyl glycol is HOR 2 OH, where R 2 is selected from C6-C20 fluorinated alkylene groups, and R 2 The proportion of carbon atoms directly connected to fluorine in the total carbon atoms is not less than 40%; The preparation method of the polyurethane grafted modified conductive filler comprises the following steps: S1, reacting the long-chain alkyl glycol and / or the fluoroalkyl glycol with a polyisocyanate to obtain an isocyanate-terminated prepolymer; S2. Disperse the conductive filler in an organic solvent to prepare a dispersion, add the isocyanate-terminated prepolymer described in step S1, react, filter, wash, and dry to obtain the product; In step S2, the weight ratio of the conductive filler, the organic solvent and the isocyanate-terminated prepolymer is 1:10-1000:0.01-0.

5.

2. The PPTC polymer composition according to claim 1, characterized in that The polyurethane of the polyurethane grafted modified conductive filler further contains a second chain segment formed by polyester polyol and / or polyether polyol, the first chain segment and the second chain segment are arranged alternately, and adjacent first chain segments and second chain segments are connected by a urethane bond.

3. The PPTC polymer composition according to claim 1, characterized in that The raw material components further contain 0.5-5 parts of auxiliary agents.

4. The PPTC polymer composition according to claim 3, characterized in that The auxiliary agent is selected from at least one of an antioxidant and a lubricant.

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