COC microcellular foam material and preparation method thereof

Abstract

The invention provides a COC microcellular foam material and a preparation method thereof. The preparation method comprises the following steps: extruding, granulating and crushing a nucleating agent and a first part of COC resin; adding a second part of COC resin, and carrying out melt blending to obtain modified COC; carrying out foaming treatment on the modified COC and a physical foaming agent to obtain a COC microcellular foaming material; wherein the nucleating agent is polytetrafluoroethylene. According to the invention, PTFE is used as a nucleating agent, so that the cell density of the prepared foam material is increased, the cell size is reduced, the cell size is homogenized, the COC cell structure can be improved, and the preparation method is simple. The COC microcellular foam material disclosed by the invention has high strength and low thermal conductivity, and meets the requirements of high-strength wall thermal insulation materials.

Description

Technical Field

[0001] The invention relates to a COC microporous foaming material and a preparation method thereof, belonging to the technical field of polymer materials. Background Art

[0002] Energy waste is inevitable in the process of energy storage, transmission, conversion, etc. In the process of energy use, by using good thermal insulation materials, the energy utilization rate can be significantly improved and energy waste can be reduced. For example, the use of highly insulated house design can reduce heat consumption by about 80% and total energy consumption by about 50%. Therefore, the strength and thermal insulation performance of the material used as wall insulation are particularly important.

[0003] Cyclic olefin copolymer (COC) is a non-crystalline transparent resin formed by copolymerizing ethylene or α-olefin with norbornene using a metallocene catalyst. It has the advantages of good chemical corrosion resistance, high thermal stability, high mechanical strength, etc., and its structure has natural thermal insulation advantages, making it a potential high-efficiency thermal insulation material. However, as a new material, the research on microporous foaming of COC is still relatively limited, which makes the selection of foaming process challenging, and the common agglomeration phenomenon in the existing technology further increases the difficulty of processing.

[0004] In view of this, it is of great significance to develop a high-strength, low-thermal conductivity COC microporous foam material, enhance the application potential of COC in the field of thermal insulation, and provide more possibilities for the efficient use of energy. Summary of the invention

[0005] In order to solve the above technical problems, the object of the present invention is to provide a COC microporous foam material and a preparation method thereof. The COC microporous foam material has high strength and low thermal conductivity.

[0006] To achieve the above object, in a first aspect, the present invention provides a method for preparing a COC microporous foam material, which comprises the following steps:

[0007] Step 1: extruding and granulating the nucleating agent and the first part of COC resin, and crushing;

[0008] Step 2: adding a second portion of COC resin for melt blending to obtain modified COC;

[0009] Step 3: The modified COC is subjected to foaming treatment with a physical foaming agent to obtain a COC microporous foaming material.

[0010] According to a specific embodiment of the present invention, preferably, the nucleating agent is polytetrafluoroethylene.

[0011] According to a specific embodiment of the present invention, preferably, in step 2, a second portion of COC resin is added for melt blending to reduce the effective content of the nucleating agent. In the modified COC, the effective content of the nucleating agent is not more than 2phr, and more preferably less than 1phr. The effective content of the nucleating agent is within the scope of the present invention, which can facilitate the introduction of nucleation points in the subsequent foaming process, improve the pore structure and enhance the mechanical properties. If the effective content of the nucleating agent in the modified COC is higher than 2phr, the fiberization effect of the nucleating agent is not good, resulting in a decrease in the performance of the COC microporous foam material.

[0012] According to a specific embodiment of the present invention, preferably, in the step 1, based on the first part of the COC resin, the amount of the nucleating agent added is ≥ 10 phr.

[0013] According to a specific embodiment of the present invention, preferably, the physical foaming agent is selected from one or a combination of two or more of nitrogen, carbon dioxide, alcohol, butane, and dimethyl ether; more preferably, the physical foaming agent is selected from carbon dioxide (CO2), which has high safety and good foaming properties.

[0014] According to a specific embodiment of the present invention, preferably, in the step 1, extrusion granulation is carried out by a twin-screw extruder, and the processing temperatures of the twin-screw extruder from the feeding section to the die are 60-70°C, 120-130°C, 200-210°C, 210-220°C, 210-220°C, 210-220°C, and 200-220°C. The present invention uses a twin-screw extruder to effectively mix and plasticize materials, the initial temperature is the feeding port temperature, 60-70°C is convenient for plasticizing the pellets, and prevents the feeding port from being blocked due to excessive temperature; the second section 120-130°C is to control the feeding port temperature and further plasticize the pellets; then reach the optimal processing temperature of 210-220°C, at which temperature the blending state of the blend system is optimal, and finally 200-220°C to ensure that the material maintains good fluidity and uniformity during extrusion.

[0015] According to a specific embodiment of the present invention, preferably, in step 1, the speed of the twin-screw extruder is 90-110 rpm, preferably 100 rpm. Controlling the speed of the twin-screw extruder within the range of the present invention can ensure uniform dispersion of the nucleating agent.

[0016] According to a specific embodiment of the present invention, preferably, in the step 2, the temperature of the melt blending is 200-220°C, the rotation speed is 50-100 rpm, and the time is 6-12 min. If the temperature of the melt blending is too low, the polymer viscosity will be too high, the extruder screw torque will increase, and there may be a risk of screw breakage. At the same time, it will also cause the blend to fail to melt completely, affecting the dispersion effect; if the temperature is too high, the polymer will accelerate oxidation and decomposition.

[0017] According to a specific embodiment of the present invention, preferably, in the step three, the modified COC is subjected to a foaming treatment with a physical foaming agent to form a homogeneous system, and is isothermally soaked at 175-185°C for 1-2.5 hours. After the soaking, the pressure is quickly released to allow the foaming agent to expand rapidly to form a foaming structure, thereby obtaining the COC microporous foam material. If the above temperature and time are not within the scope of the present invention, a foam material with a suitable ratio and good pore morphology cannot be obtained. Too low or too high a temperature will cause the ratio of the foam material to decrease rapidly.

[0018] According to a specific embodiment of the present invention, preferably, the nucleating agent and the first part of the COC resin are extruded and granulated, and a mechanical crushing device can be used to obtain smaller particles. In addition, the crushing means commonly used in the art can also be used, which is not limited by the present invention.

[0019] In a second aspect, the present invention also provides a COC microporous foam material prepared by the above-mentioned preparation method.

[0020] According to a specific embodiment of the present invention, preferably, the pore size of the COC microporous foamed material is 5-10 μm.

[0021] According to a specific embodiment of the present invention, preferably, the cell density of the COC microporous foam material is 1×10 10 -4×10 10 cells / cm 2 .

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The PTFE of the present invention is used as a nucleating agent, is first extruded and granulated with a part of the COC resin, and then melt-blended with the COC resin and foamed. The prepared foamed material has high pore density and small pore size, has the effect of homogenizing the pore size, can improve the pore structure of the COC microporous foamed material and enhance the mechanical properties. The processing technology of the PTFE of the present invention is simple and efficient, and the preparation method is simple and low in cost.

[0024] The COC microporous foam material of the present invention has high strength and low thermal conductivity, and meets the demand for high-strength wall insulation materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is the SEM image of the pore structure and pore size of the COC microporous foam material of Examples 1-2 and Comparative Example 1.

[0026] Figure 2 It is the SEM image of the pore structure and pore size of the COC microporous foam material of Examples 3-6.

[0027] Figure 3 These are the rheological property test results of the COC microporous foam materials of Examples 1-6 and Comparative Example 1.

[0028] Figure 4 It is the compression stress-strain curve of the COC microporous foam material of Examples 1-6 and Comparative Example 1.

[0029] Figure 5 It is a compression strength diagram of the COC microporous foam material of Examples 1-6 and Comparative Example 1. DETAILED DESCRIPTION

[0030] In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be construed as limiting the applicable scope of the present invention.

[0031] The performance measurement process of the COC microporous foam material in the embodiment of the present invention includes the following aspects:

[0032] 1. Cell size: The cell size is obtained by analyzing the photos of the cell morphology in the SEM using graphic analysis software and performing statistical calculations.

[0033] 2. Density: Tested according to ASTM D792-2000 (i.e., drainage method). Under the same conditions, at least 6 samples were selected for testing and the average value was taken.

[0034] 3. Foaming ratio: Calculate the ratio of the average density of the unfoamed sample to the density of the foamed product.

[0035] 4. Mechanical test of matrix material: The tensile strength is tested according to the ASTM D638 standard, and at least 5 parallel samples are selected; the notched impact strength is tested according to the ISO 179-1 standard, and 10 parallel samples are selected for each set of data.

[0036] 5. Rheological properties test of matrix material: Use a rotational rheometer to perform strain scanning mode and frequency scanning test on the sample. Take a sample with a diameter of 20mm and a thickness of 1mm, place it in a parallel plate fixture, and the test temperature is 220℃; the shear angle frequency range is 0.1-100Hz; the strain range is 1%-10%.

[0037] 6. Foam mechanical properties test: It is carried out at room temperature. All foam samples (foaming materials) have the same foaming ratio (about 5-6 times), the size is 10mm×10mm×10mm, and the compression speed is 1mm / min.

[0038] 7. Thermal conductivity test: The thermal conductivity was calculated using a thermal constant analyzer HOT DISK (Thermal Test Inc., TPS2500, Sweden). The foam material was made into a square sample of 2 cm × 2 cm × 5 mm, the output power was 6 mW, the sensor size was 3 mm, and the test duration was 10 s.

[0039] Embodiment 1:

[0040] This embodiment provides a method for preparing a COC microporous foam material, wherein the raw materials include the following components:

[0041] COC resin: 50g;

[0042] PTFE nucleating agent: 0.125 g;

[0043] The preparation method comprises the following steps:

[0044] Step 1: Add 0.125 g of PTFE nucleating agent to 1.25 g of COC resin (the first part of COC resin), and extrude and granulate by a twin-screw extruder. The processing temperatures from the feeding section to the die of the twin-screw extruder are 60°C, 120°C, 200°C, 210°C, 210°C, 200°C, respectively. The twin-screw speed is 100 rpm, and the obtained sample is crushed;

[0045] Step 2: Add the remaining COC resin to the above sample so that the effective content of the PTFE nucleating agent is not more than 2phr, and perform secondary blending using a torque rheometer at a blending temperature of 220° C., a blending speed of 100 rpm, and a blending time of 10 min to obtain a modified COC;

[0046] Step 3: Introduce the blowing agent CO2 into the modified COC to form a homogeneous system, then isothermally soak at 185°C for 1 hour and then release the pressure instantly to obtain a COC microporous foam material, recorded as COC / PTFE-0.25.

[0047] Embodiment 2:

[0048] This embodiment provides a method for preparing a COC microporous foam material, which differs from Embodiment 1 only in that:

[0049] The raw materials contain the following qualities:

[0050] COC resin: 50g;

[0051] PTFE nucleating agent: 0.25g;

[0052] The prepared COC microporous foam material is recorded as COC / PTFE-0.5.

[0053] Embodiment 3:

[0054] This embodiment provides a method for preparing a COC microporous foam material, which differs from Embodiment 1 only in that:

[0055] The raw materials contain the following qualities:

[0056] COC resin: 50g;

[0057] PTFE nucleating agent: 0.375 g;

[0058] The prepared COC microporous foam material is recorded as COC / PTFE-0.75.

[0059] Embodiment 4:

[0060] This embodiment provides a method for preparing a COC microporous foam material, which differs from Embodiment 1 only in that:

[0061] The raw materials contain the following qualities:

[0062] COC resin: 50g;

[0063] PTFE nucleating agent: 0.5g;

[0064] The prepared COC microporous foam material is recorded as COC / PTFE-1.

[0065] Embodiment 5:

[0066] This embodiment provides a method for preparing a COC microporous foam material, which differs from Embodiment 1 only in that:

[0067] The raw materials contain the following qualities:

[0068] COC resin: 50g;

[0069] PTFE nucleating agent: 0.75g;

[0070] The prepared COC microporous foam material is recorded as COC / PTFE-1.5.

[0071] Embodiment 6:

[0072] This embodiment provides a method for preparing a COC microporous foam material, which differs from Embodiment 1 only in that:

[0073] The raw materials contain the following qualities:

[0074] COC resin: 50g;

[0075] PTFE nucleating agent: 1g;

[0076] The prepared COC microporous foam material is recorded as COC / PTFE-2.

[0077] Comparative Example 1

[0078] This comparative example provides a method for preparing a COC microporous foam material, wherein the raw materials include the following components by mass:

[0079] COC resin: 50g;

[0080] The preparation method comprises the following steps:

[0081] Step 1: Extruding the COC resin into granules through a twin-screw extruder, the processing temperatures of the twin-screw extruder from the feeding section to the die are: 60°C, 120°C, 200°C, 210°C, 210°C, 210°C, 200°C, and the twin-screw speed is 100rpm, and the obtained sample is crushed;

[0082] Step 2: Blending was performed using a torque rheometer at a blending temperature of 220° C., a blending speed of 100 rpm, and a blending time of 10 min to obtain a modified COC;

[0083] Step 3: Introduce the blowing agent CO2 into the modified COC to form a homogeneous system, then isothermally soak at 185°C for 1 hour and then release the pressure instantly to obtain a COC microporous foam material, which is recorded as COC / PTFE-0.

[0084] Comparative Example 2

[0085] This comparative example provides a method for preparing a composite foam material, which differs from Example 2 only in that:

[0086] The raw materials contain the following qualities:

[0087] PA12T: 50g;

[0088] PTFE nucleating agent: 0.25g;

[0089] In order to obtain a similar ratio (about 5-6 times) as the foaming material in Example 1, the soaking temperature was 255°C;

[0090] The obtained foamed material was recorded as PA12T / PTFE-0.5.

[0091] Comparative Example 3

[0092] This comparative example provides a method for preparing a composite foam material, which differs from Example 2 only in that:

[0093] The raw materials contain the following qualities:

[0094] PLA: 50g;

[0095] PTFE nucleating agent: 0.25g;

[0096] In order to obtain a similar ratio (about 5-6 times) to the foaming material in Example 1, the soaking temperature was 165°C;

[0097] The obtained foamed material was recorded as PLA / PTFE-0.5.

[0098] Comparative Example 4

[0099] This comparative example provides a method for preparing a composite foam material, which differs from Example 2 only in that:

[0100] The raw materials contain the following qualities:

[0101] PP: 50g;

[0102] PTFE nucleating agent: 0.25g;

[0103] In order to obtain a similar ratio to that of the foaming material in Example 1 (about 5-6 times), the soaking temperature was 185°C;

[0104] The obtained foamed material was recorded as PP / PTFE-0.5.

[0105] Comparative Example 5

[0106] This comparative example provides a method for preparing a composite foam material, which differs from Example 2 only in that:

[0107] The raw materials contain the following qualities:

[0108] COC: 50g;

[0109] SiO2 nucleating agent: 0.25g;

[0110] In order to obtain a similar ratio to that of the foaming material in Example 1 (about 5-6 times), the soaking temperature was 185°C;

[0111] The foamed material was obtained and recorded as COC / SiO2-0.5.

[0112] Comparative Example 6

[0113] This comparative example provides a method for preparing a composite foam material, which differs from Example 2 only in that:

[0114] The raw materials contain the following qualities:

[0115] COC: 50g;

[0116] CNT nucleating agent: 0.25g;

[0117] In order to obtain a similar ratio (about 5-6 times) as the foaming material in Example 2, the soaking temperature was 185°C;

[0118] The foamed material was obtained and recorded as COC / CNT-0.5.

[0119] Comparative Example 7

[0120] This comparative example provides a method for preparing a COC microporous foam material, which differs from Example 1 only in that:

[0121] In step three, a blowing agent CO2 is introduced into the modified COC to form a homogeneous system, and then the pressure is released instantaneously after isothermal soaking at 195°C for 1 hour to obtain a COC microporous foam material.

[0122] Comparative Example 8

[0123] This comparative example provides a method for preparing a COC microporous foam material, which differs from Example 1 only in that:

[0124] In step three, a blowing agent CO2 is introduced into the modified COC to form a homogeneous system, and then the pressure is released instantaneously after isothermal soaking at 205°C for 1 hour to obtain a COC microporous foam material.

[0125] The expansion ratio and cell structure of the above examples and comparative examples are shown in Table 1.

[0126] Table 1

[0127]

[0128] As can be seen from Table 1, the foam material obtained by using COC resin and PTFE nucleator in the embodiment has the effect of high cell density, small cell size and homogenization of cell size, which effectively improves the COC cell structure. Specifically, the thermal conductivity of the foam material obtained in Examples 1-6 changes with the change of PTFE content. According to Table 1, it can be seen that when the PTFE nucleator content is 0.5phr, the thermal conductivity is the lowest, which shows that the nucleation effect at this time is the best, and the cell size reaches the minimum. And Comparative Examples 2-4 are other resins and PTFE blends, and the thermal conductivity of the foam material obtained is higher than the thermal conductivity of the embodiment, indicating that the foam material obtained by using COC resin of the present invention and PTFE nucleator blends has high strength, low thermal conductivity, and simple processing technology, COC does not absorb water and does not degrade, does not need to dry, and has a long storage time.

[0129] Comparative Examples 5 and 6 are foaming materials made of COC resin and other nucleating agents, and the cell density of Example 2 is 3.86×10 10 cells / cm 2 In comparison, the cell density of Comparative Examples 5 and 6 is smaller, which proves that the foamed material prepared by blending the COC resin of the present invention with the PTFE nucleating agent has more excellent performance.

[0130] In step 3 of Comparative Examples 7 and 8, the immersion temperature is higher than the range of the present invention, and compared with Example 1, the ratio of the foaming material of Comparative Examples 7 and 8 is greatly reduced.

[0131] The SEM images of the cell structures and cell size diagrams of Examples 1-6 and Comparative Example 1 of the present invention are as follows: Figure 1-Figure 2 As shown, Figure 1 Figures (a) and (a1) are the correlation diagrams of Comparative Example 1. Figure 1 Figures (b) and (b1) are related diagrams of Example 1. Figure 1 Figures (c) and (c1) are related diagrams of Example 2; Figure 2 Figures (d) and (d1) are related diagrams of Example 3. Figure 2 Figures (e) and (e1) are related diagrams of Example 4. Figure 2 Figures (f) and (f1) are related diagrams of Example 5. Figure 2 Figures (g) and (g1) in the figure are related figures of Example 6. It can be seen from the figure that the use of PTFE as a nucleating agent can increase the cell density, reduce the cell size, and homogenize the cell size, which shows that the PTFE nucleating agent can improve the cell structure of COC. This is because the highly crystalline PTFE powder particles and the thermoplastic polymer COC resin are deformed and entangled during the processing. The PTFE powder particles undergo lattice slip deformation under the action of shear stress and tensile stress to become initial fiber bundles with a certain aspect ratio. These fiber bundles are further deformed under the action of continuous stretching and shear stress, entangled with each other, and finally extended into a nanofiber network.

[0132] Figure 3 The rheological properties test results of the COC microporous foam materials of Examples 1-6 and Comparative Example 1 are shown in FIG. Figure 3In the figure above, the storage modulus (G') starts in the low frequency region and increases with the increase of PTFE content, indicating that after melt blending of COC resin and PTFE, the unfoamed modified COC has high melt strength and good expandability; when it is increased to the optimal component content, that is, the addition amount of nucleating agent in Example 2 is 0.5phr, the storage modulus decreases with the increase of PTFE content, which indicates that PTFE has agglomerated and the improvement effect on the rheological properties of the matrix material of COC resin has weakened. Figure 3 As can be seen from the figure below, the increase in complex viscosity (η*) further shows that in the low-frequency region, with the increase of PTFE content, the complex viscosity first increases and then decreases. This is because low-content PTFE will form fibers. With the increase of PTFE content, PTFE fibers entangle with each other to form a 3D fiber network. After exceeding the optimal content, continuing to increase PTFE will cause PTFE to agglomerate and destroy the fiber network structure. In the high-frequency region, the complex viscosity of the component with PTFE added is lower than that of the component without PTFE added. This is because there is a fiber network in the low-frequency region. The more fiber networks there are, the more entanglement points there are, and the higher the viscosity. In the high-frequency region, the fiber network is disentangled, and PTFE has a lubricating effect, which reduces the viscosity of the blend system.

[0133] Figure 4 The compressive stress-strain curves of the COC microporous foam materials in Examples 1-6 and Comparative Example 1 show that as the PTFE content increases, the mechanical strength of the foam material increases first and then decreases. Figure 3 It is proved that the addition of PTFE can improve the mechanical properties of foam by improving the pore structure.

[0134] Figure 5 This is a compression strength diagram of the COC microporous foam material in Examples 1-6 and Comparative Example 1. It can be seen that with the increase of PTFE, the compression strength is also significantly improved, which is conducive to meeting the demand for high-strength wall insulation materials.

Claims

1. A method for preparing a COC microporous foam material, wherein: The following steps are involved: Step 1: extruding and granulating the nucleating agent and the first part of COC resin, and crushing; Step 2: adding a second portion of COC resin for melt blending to obtain modified COC; Step 3: The modified COC is subjected to foaming treatment with a physical foaming agent to obtain a COC microporous foaming material; Wherein, the nucleating agent is polytetrafluoroethylene.

2. The preparation method according to claim 1, wherein In the step 1, based on the first part of the COC resin, the amount of the nucleating agent added is ≥10 phr.

3. The preparation method according to claim 1, wherein In the step 2, in the modified COC, the effective content of the nucleating agent is not more than 2 phr, preferably less than 1 phr.

4. The preparation method according to claim 1, wherein The physical foaming agent is selected from one or a combination of two or more of nitrogen, carbon dioxide, alcohol, butane, and dimethyl ether; Preferably, the physical blowing agent is selected from carbon dioxide.

5. The preparation method according to claim 1, wherein In the step one, extrusion granulation is carried out by a twin-screw extruder, and the processing temperatures set from the feeding section to the die of the twin-screw extruder are 60-70°C, 120-130°C, 200-210°C, 210-220°C, 210-220°C, 210-220°C, 200-220°C, and the rotation speed of the twin-screw extruder is 90-110rpm, preferably 100rpm.

6. The preparation method according to claim 1, wherein In the step 2, the temperature of the melt blending is 200-220° C., the rotation speed is 50-100 rpm, and the time is 6-12 min.

7. The preparation method according to claim 1, wherein In the step three, the temperature during the foaming treatment is 175-185° C. and the time is 1-2.5 hours.

8. A COC microporous foam material obtained by the preparation method according to any one of claims 1 to 7.

9. The COC microporous foam material according to claim 8, wherein: The pore size of the COC microporous foam material is 5-10 μm.

10. The COC microporous foam material according to claim 8, wherein: The cell density of the COC microporous foam material is 1×10 10 -4×10 10 cells / cm 2 .

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