CN113337035A

CN113337035A - High-thermal-conductivity low-dielectric polypropylene continuous composite sheet composition and preparation method thereof

Info

Publication number: CN113337035A
Application number: CN202011198325.7A
Authority: CN
Inventors: 彭珂; 林汉卿; 王婷
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-10-31
Filing date: 2020-10-31
Publication date: 2021-09-03

Abstract

The invention provides a high-thermal-conductivity low-dielectric polypropylene composite continuous sheet composition, and the composite sheet has excellent dielectric property and mechanical property. The low dielectric polypropylene continuous composite sheet provided by the invention comprises the following raw materials in percentage by mass: 20-70% of fibrous filler: 10% -60% of heat-conducting filler: 0% -15% of a toughening agent: 0% -20% of an ultraviolet absorber: 0% -1% of antioxidant: 0% -1% of coupling agent: 0 to 5 percent.

Description

High-thermal-conductivity low-dielectric polypropylene continuous composite sheet composition and preparation method thereof

Technical Field

The present disclosure relates to thermoplastic compositions for communication applications, and in particular to polypropylene thermoplastic compositions having relatively low dielectric constants and low dielectric losses.

Background

Polypropylene (PP) has the advantages of light weight, easy processing and easy molding, and plastic is widely used in automobiles, household electrical appliances, hand-held electric tools and the like, in addition, PP resin is a non-polar resin, has weak polarization capability and excellent dielectric property, has a dielectric constant (Dk) between 2.1 and 2.3, a dielectric loss (Df) value which is extremely small and less than 0.0005, and an electromagnetic wave frequency of 1MHz, and therefore can be used for preparing outer covers of electronic communication products, but polypropylene resin has low mechanical property and usually needs to be reinforced by adding glass fiber in the using process. Since Dk and Df of the common glass fiber, namely E-glass, are high, the Dk value is 6.6-6.8, and the Df value is 0.005, the dielectric property of the PP composite material can be deteriorated, and the application of the PP composite material in the field of electronic communication is further influenced, so that the development of the PP composite material with low Dk and low Df has important significance for promoting the wide application of the PP composite material in the field of electronic communication, especially the 5G field.

At present, the technical route of low dielectric PP composite materials is mainly realized by adding Dk and Df dual-low dielectric fillers into PP resin, as reported in patents CN110684274A, CN109312113A and CN106543554A, when short-cut glass fibers with Dk less than 5.0 and Df less than 0.002 are added into PP resin, Dk and Df are respectively less than 2.8 and 0.003, and when the frequency of electromagnetic wave is 1GHz-5 GHz. Patent CN111154188A reports that hollow glass beads are added into PP resin to prepare low dielectric PP composite material, while patent CN109206751A adopts a technical route combining Dk value less than 5.0 and hollow cage type silsesquioxane. Patent CN107141686A discloses a low dielectric constant polypropylene material modified by low dielectric glass fiber and doped silica.

In the aspect of the preparation process technology of the thermoplastic low-dielectric PP composite material, a twin-screw extrusion granulation process and a long glass fiber reinforced PP resin (LFT) process technology are adopted, and patents CN111117070A, CN111073148A and CN105367897A are reported.

Although the production of low dielectric PP composites is possible using the above-mentioned technical route, there still remains the problem that 1) low dielectric glass fibers that achieve Dk less than 5.0 currently on the market are not yet available on a large scale due to their high price. 2) The special polymer fiber has high manufacturing cost, heat-resistant temperature lower than that of glass fiber, poor compatibility with polyolefin and unattractive application prospect in low-dielectric PP composite materials. 3) The hollow glass beads can introduce air into the material theoretically, and are favorable for reducing the dielectric constant of the material. But the hollow glass beads are damaged in the double-screw extrusion process, and the hollow glass beads have no length-diameter ratio, so that the requirement on the extrusion process is high, and the mechanical property of the PP resin after being added cannot be obviously improved. 4) Both chopped glass fiber and long glass fiber reinforced PP composite materials have low impact strength, so that the application of the composite materials in low-temperature environments and large-scale housing shell parts is limited. 5) The dielectricity of the PP composite material in the patent publication only relates to the frequency of electromagnetic waves within 5GHz, and is not mentioned in the part above 5GHz, and when the frequency of the electromagnetic waves is more than 5GHz, the stable dielectricity of the material is important for practical application under high-frequency conditions. In addition, for the future 5G high frequency communication, the heat dissipation of the communication electronic equipment is also an urgent problem to be solved.

In summary, in order to overcome the above disadvantages and meet the new requirements of the 5G communication market for materials, a low dielectric PP composite material with stable dielectric property and excellent thermal conductivity and mechanical property under high frequency is developed and designed, and has a wide application prospect in the 5G communication field.

Disclosure of Invention

The invention firstly provides a high-thermal-conductivity low-dielectric polypropylene composite continuous sheet composition, and the composite sheet has excellent dielectric property and mechanical property.

The low dielectric polypropylene continuous composite sheet provided by the invention is characterized by comprising the following raw materials in percentage by mass

Polypropylene: 20 to 70 percent

Fiber filler: 10 to 60 percent

Heat-conducting filler: 0 to 15 percent

A toughening agent: 0 to 20 percent

Ultraviolet absorber: 0 to 1 percent

Antioxidant: 0 to 1 percent

Coupling agent: 0 to 5 percent

Preferably, the polypropylene is present in an amount of 10% to 70%, more preferably 15% to 65%, and most preferably 20% to 60%. The polypropylene is one or a mixture of more of homopolymerized polypropylene, copolymerized polypropylene or flame-retardant modified polypropylene, and the melt index of the polypropylene is more than 100g/10min under the condition of 230 ℃/2.16 kg.

Preferably, the fibrous filler has a dielectric constant and a dielectric loss of less than 5.5 and less than 0.005, respectively, at a frequency of 1 GHz. The fiber filler is a fiber fabric, the fiber fabric is one or a mixture of more than two of a checkered cloth, a fine woven fabric and a fiber felt, and the gram weight of the fabric is less than 1000g/m²And the thickness is less than 0.5 mm. The fiber filler is one or a composition of more of glass fiber, basalt fiber, quartz fiber and aramid fiber. The fiber is glass fiber with the diameter of 4-22 microns, and the cross section of the glass fiber is circular, irregular or the combination of the circular and the irregular.

Preferably, the fiber content is from 10% to 60%, more preferably from 20% to 50%.

Preferably, the fibers have a diameter of 5-21um, more preferably 9-14 um.

Preferably, the content of the thermally conductive filler is 5% to 30%, more preferably 10% to 25%. The heat conducting filler is one or a combination of boron nitride, silicon nitride, aluminum nitride, silicon carbide and aluminum oxide, and the shape of the heat conducting filler is lamellar, spherical or a combination of the two.

Preferably, the particle size of the thermally conductive filler is 10 to 50um, more preferably 10 to 40 um.

Preferably, the content of the toughening agent is 0% to 20%, more preferably 5% to 15%. The toughening agent is one or a composition of more of a rubber toughening agent, a polyolefin elastomer toughening agent and a maleic acid grafted polyethylene toughening agent.

Preferably, the content of the ultraviolet absorbent is 0% -1%, more preferably 0.1% -0.3%, and the ultraviolet absorbent is one or two mixtures of benzotriazoles and benzophenones.

Preferably, the antioxidant is present in an amount of 0% to 1%, more preferably 0.1% to 0.5%. The antioxidant is one or a composition of more of hindered phenol antioxidant, phosphite antioxidant and thioester antioxidant.

Preferably, the content of the coupling agent is 0% -5%, more preferably 2% -5%, and the coupling agent is a maleic anhydride grafted polypropylene raw material, and the maleic anhydride grafting rate of the coupling agent is not less than 1.0%.

The invention further relates to a preparation method of the composite sheet. The method comprises the following steps:

(1) firstly, extruding and granulating PP granules or powder, heat-conducting filler and all auxiliaries by a double-screw extruder, drying, controlling the extrusion temperature to be 190-230 ℃, preparing the obtained modified polypropylene resin granules into a 0.1mm polypropylene matrix film on a tablet press, wherein the temperature of the tablet press is 190-220 ℃, and the pressure is 7-9 MPa;

(2) cutting the polypropylene matrix film and the fiber fabric prepared in the step (1) into a large width of 1-2m

Small, and stacked into a sandwich structure, two layers of polypropylene films, and a glass fiber fabric structure layer arranged between the two polypropylene films, wherein the total thickness of the sandwich structure can be adjusted by the number of layers of the films and the glass fiber fabric;

(3) and (3) putting the sandwich structure in the step (2) into a double-steel-belt press for hot pressing, wherein the hot pressing temperature is 200-250 ℃, the hot pressing pressure is 7-10MPa, and the running speed of the steel belt is 1-3m/min, so as to prepare the composite material sheet.

The obtained composite material sheet has a dielectric constant of less than 3.0 and a dielectric loss tangent of less than 0.004 under the condition that the frequency of electromagnetic waves is more than 5 GHz.

The prepared low dielectric polypropylene composite continuous sheet is applied to the communication field.

Compared with the prior art, the PP composite sheet composition and the preparation method provided by the invention have the following beneficial effects:

the low-dielectric PP composite sheet material has excellent dielectric property, so that the low-dielectric PP composite sheet material can be applied to the field of high-frequency electronic communication, and meanwhile, compared with the existing low-dielectric PP material, the low-dielectric PP composite sheet material has more excellent mechanical property.

Detailed Description

For a further understanding of the invention, reference will now be made to the preferred embodiments of the invention by way of example, and it is to be understood that the description is intended to further illustrate features and advantages of the invention, and not to limit the scope of the claims.

EXAMPLES starting materials

Polypropylene: YJP-3100H, Yangzhiti petrochemical

Low-dielectric glass fiber fabric: HL2116, Shanghai-Tian atlantoan Material science and technology Co., Ltd

Ordinary glass fiber fabric: 2116 atlas materials science and technology, Shanghai

Basalt fiber fabric: zhejiang Shijin basalt fiber Co Ltd

Low dielectric chopped glass fiber: ECS305-3-K/HL, Chongqing International composite Co., Ltd

Boron nitride: suzhou brocade new material science and technology limited, particle size 40um (D50)

Aluminum nitride: TFZ-S30P, Toyo aluminum Co., Ltd., Japan, particle size 30um (D50)

A toughening agent: ENGAGE^TM8003 Dow chemical

Ultraviolet absorber: UV-531, BASF

Antioxidant: phenolic antioxidants, 1010BASF

Coupling agent: maleic anhydride grafted Polypropylene OREVAC CA100, Acoma

Examples 1 to 10

According to the mass percentage shown in the table 1, extruding and granulating the PP resin, the heat-conducting filler, the antioxidant, the ultraviolet absorbent, the toughening agent and the coupling agent by using a single-screw extruder, drying, controlling the extrusion temperature to be 190-230 ℃, preparing the obtained modified polypropylene resin granules into a 0.1mm polypropylene matrix film on a tablet press, controlling the temperature of the tablet press to be 190-220 ℃ and controlling the pressure to be 7-9 MPa;

cutting the polypropylene matrix film and the fiber fabric prepared in the step (1) into pieces with the width of 1m, placing a layer of fiber fabric between two layers of PP films, and sending the pieces into a double-steel-belt press for hot pressing, wherein the hot pressing temperature is 210 ℃ and 250 ℃, the hot pressing pressure is 7-10MPa, and the running speed of a steel belt is 1-3m/min, so as to prepare the PP composite material sheets with different fiber contents.

Comparative examples 1 to 2

The main difference between the examples and the comparative examples is the choice of the fibrous filler, which is a low dielectric constant and lossy fibrous fabric in examples 1-10, and a plain glass fiber fabric in the comparative examples.

Comparative examples 3 to 4

According to the mass percentage shown in table 1, the PP resin, the heat-conducting filler, the antioxidant 1010, the coupling agent, the ultraviolet absorbent and the toughening agent are put into a high-speed mixer for mixing, then the mixed material is added into a double-screw extruder through a main feeding port of the double-screw extruder, and finally the low-dielectric glass fiber is added into the double-screw extruder through a side feeding port of the double-screw extruder according to the required proportion for granulation. In the whole processing process, the processing temperature of the extruder is controlled at 230 ℃ and the rotation speed of the twin screw is 300 r/min.

Specific component ratios of the above examples and comparative examples are shown in Table 1

Table 1

The materials obtained in the examples and comparative examples were subjected to the test of samples required for the standard preparation of mechanical property test and dielectric property test, and the test results are shown in Table 2 and Table 3, respectively.

Table 2

Test items	Test standard
		Tensile strength of sheet material	ISO527-5
Tensile modulus of sheet material	ISO527-5
		Bending strength of plate	ISO14125
Unnotched impact strength of plate	ISO179
		Tensile strength of plastic	ASTM D638
Tensile modulus of plastics	ASTM D638
		Bending strength of plastic	ASTM D790
Unnotched impact strength of plastic	ASTM D256
		Dielectric properties (Low frequency)	IEC61189-2-721
Dielectric properties (high frequency)	ASTM-D2520
		Coefficient of thermal conductivity	ASTM D5470

The test results of the embodiment and the comparative example show that the continuous composite sheet prepared by the technical scheme of the invention has more excellent mechanical property, dielectric property and heat-conducting property compared with the polypropylene composite material with the same composition prepared by twin-screw extrusion molding.

Table 3

The above embodiments are only exemplary embodiments of the present invention, and are not intended to limit the present invention, and the scope of the present invention is defined by the claims. Various modifications and equivalents may be made by those skilled in the art within the spirit and scope of the invention.

Claims

1. The high-thermal-conductivity low-dielectric polypropylene continuous composite sheet is characterized by comprising the following raw materials in percentage by mass

Polypropylene: 20 to 70 percent

Fiber filler: 10 to 60 percent

Heat-conducting filler: 0 to 15 percent

A toughening agent: 0 to 20 percent

Ultraviolet absorber: 0 to 1 percent

Antioxidant: 0 to 1 percent

Coupling agent: 0 to 5 percent.

2. The continuous composite sheet of claim 1, wherein the continuous composite sheet has a dielectric constant of less than 3.0 and a dielectric loss tangent of less than 0.004 at a frequency of electromagnetic waves of more than 5 GHz.

3. The continuous composite sheet material of claim 1, wherein the polypropylene is a mixture of one or more of homo-polypropylene, co-polypropylene or flame retardant modified polypropylene, and the melt index of the polypropylene is greater than 100g/10min at 230 ℃/2.16 kg.

4. The high thermal conductivity low dielectric polypropylene continuous composite sheet of claim 1The fiber filler is characterized in that the fiber filler is a fiber fabric, the fiber fabric is one or a mixture of more than two of a check cloth, a fine woven fabric and a fiber felt, and the gram weight of the fabric is less than 1000g/m²And the thickness is less than 0.5 mm.

5. The continuous composite sheet of claim 4, wherein the fibrous filler is a combination of one or more of glass fibers, basalt fibers, quartz fibers, and aramid fibers.

6. The continuous composite sheet of claim 4, wherein the fiber filler has a dielectric constant and a dielectric loss of less than 5.5 and less than 0.005, respectively, at an electromagnetic frequency of 1 GHz; the fiber is glass fiber with the diameter of 4-22 microns, and the cross section of the glass fiber is circular, irregular or the combination of the circular and the irregular.

7. The continuous composite sheet of claim 1, wherein the thermally conductive filler is one or more of boron nitride, silicon nitride, aluminum nitride, silicon carbide and aluminum oxide, the particle size of the thermally conductive filler is 10-50 μm, and the shape of the thermally conductive filler is lamellar, spherical or a combination thereof.

8. The continuous composite sheet of claim 1, wherein the antioxidant is one or more selected from the group consisting of hindered phenolic antioxidants, phosphite antioxidants, and thioester antioxidants; the toughening agent is one or a composition of more of a rubber toughening agent, a polyolefin elastomer toughening agent and a maleic acid grafted polyethylene toughening agent; the ultraviolet absorbent is one or a mixture of two of benzotriazoles and benzophenones; the coupling agent is a polypropylene raw material grafted by maleic anhydride, and the grafting rate of the maleic anhydride is not less than 1.0%.

9. A preparation method of a low dielectric polypropylene composite continuous sheet comprises the following steps:

(1) extruding and granulating the polypropylene granules or powder, the heat-conducting filler and the auxiliary agent, and then preparing a polypropylene matrix film, wherein the auxiliary agent comprises 0-4 of a toughening agent, an antioxidant, an ultraviolet absorbent and a coupling agent;

(2) stacking the polypropylene matrix film and the fiber fabric prepared in the step (1) into a sandwich structure, wherein a fiber fabric structure layer is arranged between two layers of polypropylene matrix films;

(3) hot-pressing the one or more layers of sandwich structures prepared in the step (2) to prepare the low-dielectric polypropylene composite continuous sheet;

the raw materials are calculated according to mass percentage

Polypropylene: 20 to 70 percent

Fiber filler: 10 to 60 percent

Heat-conducting filler: 0 to 15 percent

A toughening agent: 0 to 20 percent

Ultraviolet absorber: 0 to 1 percent

Antioxidant: 0 to 1 percent

Coupling agent: 0 to 5 percent.

10. Use of the low dielectric polypropylene composite continuous sheet prepared according to claim 9 in the field of communications.