A SMMA microcellular foaming material with high toughness and its preparation method

Abstract

The present invention discloses a high-toughness SMMA microcellular foaming material and a preparation method thereof. The notched impact strength of the high-toughness SMMA microcellular foaming material is above 2 KJ / m<supgt;2< / supgt>, the elongation at break is greater than 2.5%, the weight loss rate is above 25%, the average cell size is less than 40 microns, and the cell density is greater than 10<supgt;7< / supgt> cells / cm<supgt;3< / supgt>. The preparation method includes: blending and extruding 60wt% - 90wt% of SMMA, 10wt% - 40wt% of elastomer SBS, and 0 - 5wt% of nucleating agent through a twin-screw extruder. After the obtained composite material is dried, it is added into a foam injection molding machine. The foaming gas pressure is 4 - 10 MPa, and pre-plasticization is carried out to obtain a homogeneous melt of the composite material and a melt of gas. Then it is injected into the mold cavity, pressure is maintained, and then the mold is opened for foaming, and after cooling, the high-toughness SMMA microcellular foaming material is obtained.

Description

Technical Field

[0001] The present invention relates to the field of polymer materials, and particularly to a high-toughness SMMA microcellular foaming material and a preparation method thereof. Background Art

[0002] With the increasing aggravation of environmental pollution and the decreasing oil reserves, scientific researchers have been thinking about how to reduce the consumption of oil. As a material mainly extracted from oil, polymer materials not only cause serious environmental pollution but also rapidly consume precious oil resources.

[0003] So far, there are mainly two means to solve this problem. The first is to use bio-based degradable materials to replace petroleum-based polymer materials. However, due to the limitations of the development of science and technology, although materials such as polylactic acid (PLA) have developed rapidly, it is still difficult to replace a large amount of currently used petroleum-based polymer materials. The second is to use foamed materials to replace solid unfoamed materials, which can not only achieve the purpose of reducing the amount of raw materials but also realize lightweight, thereby reducing energy consumption.

[0004] Regarding the preparation methods of foamed materials, they can be mainly divided into physical foaming and chemical foaming. The gases mainly used in physical foaming are nitrogen or carbon dioxide. Due to their non-toxic and harmless nature and good cell morphology prepared, it has great advantages compared with chemical foaming.

[0005] Regarding physical foaming, according to different foaming methods, it can be mainly divided into autoclave foaming, extrusion foaming and injection foaming. Among them, injection foaming, as a semi-continuous foaming method, plays an irreplaceable role in the preparation of foamed material structural parts.

[0006] So far, injection foaming mainly relies on high-pressure injection foaming with the MuCell system as the core, usually reaching a pressure of 15 - 30 MPa, while the low-pressure foaming used in the present invention is 4 - 10 MPa, which has obvious advantages over high-pressure injection foaming in terms of equipment cost and safety.

[0007] Styrene dimethyl methacrylate copolymer (SMMA) has a series of advantages such as high strength, easy processing, high surface gloss and easy color matching. However, due to the limitations of its molecular structure, its toughness is extremely poor, which greatly limits the application of SMMA. For SMMA, due to its extremely poor toughness, energy dissipation mainly occurs in the form of crazes, and it has very poor compatibility with common elastomers such as POE, so it is very difficult to induce a shear yield band in the SMMA matrix, thereby dissipating a large amount of energy.

[0008] Generally speaking, for polymer foam materials, with the improvement of the cell structure, that is, the decrease of cell size and the increase of cell density, their toughness will gradually improve. The improvement of the cell structure mainly depends on the melt strength of the foam material. However, the melt strength of SMMA is relatively low, making it difficult to obtain a good cell structure. In the present invention, by adding a suitable elastomer, both the foaming behavior of SMMA and its toughness can be significantly improved. Summary of the Invention

[0009] The present invention provides a high-toughness SMMA microcellular foaming material, which is obtained by physically foaming a blend of styrene-butadiene-styrene block copolymer (SBS) and SMMA at a low air pressure of 4 - 10 MPa. The introduction of SBS significantly improves the toughness and cell structure of the material. The cell size of the foaming material is further reduced, and the cell density is further increased.

[0010] A high-toughness SMMA microcellular foaming material, the notched impact strength of the high-toughness SMMA microcellular foaming material is above 2 KJ / m 2 and above, and the elongation at break is greater than 2.5%;

[0011] The weight loss rate of the high-toughness SMMA microcellular foaming material is above 25%;

[0012] The average cell size of the high-toughness SMMA microcellular foaming material is less than 40 microns, and the cell density is greater than 10 7 cells / cm 3 .

[0013] The present invention also provides a preparation method of the high-toughness SMMA microcellular foaming material, including the steps:

[0014] (1) Mix 60wt% - 90wt% of SMMA, 10wt% - 40wt% of the elastomer SBS, and 0 - 5wt% of a nucleating agent through a twin-screw extruder at 150 - 230 °C to obtain a composite material;

[0015] (2) After drying the composite material obtained in step (1), add it to a foaming injection molding machine. The screw temperature is 190 - 230 °C, the mold temperature is 40 - 100 °C, the material storage speed is 5 - 60 rpm, the foaming gas pressure is 4 - 10 MPa, pre-plasticize the composite material to obtain a uniform melt of the composite material and a melt of the gas, and inject it into the mold cavity under the conditions of an injection speed of 50 - 100 mm / s and an injection pressure of 40 - 100 MPa. Keep the pressure at 40 - 100 MPa for 0.5 - 5 s, and then open the mold for foaming;

[0016] (3)Cool the sample obtained by mold opening and foaming to obtain the SMMA microcellular foaming material with high toughness.

[0017] In a preferred example, in the preparation method of the SMMA microcellular foaming material with high toughness, in step (1), the nucleating agent is an inorganic nucleating agent.

[0018] In a preferred example, in the preparation method of the SMMA microcellular foaming material with high toughness, in step (1), the nucleating agent includes at least one of talcum powder and calcium carbonate.

[0019] In a preferred example, in the preparation method of the SMMA microcellular foaming material with high toughness, in step (1), the extrusion speed is 40 - 100 rpm.

[0020] In a preferred example, in the preparation method of the SMMA microcellular foaming material with high toughness, in step (2), the drying temperature is 75 - 85 °C and the time is 6 - 8 h.

[0021] In a preferred example, in the preparation method of the SMMA microcellular foaming material with high toughness, in step (2), the foaming gas is nitrogen or carbon dioxide.

[0022] In a preferred example, in the preparation method of the SMMA microcellular foaming material with high toughness, in step (2), the mold opening distance is 1 - 3 mm.

[0023] In a preferred example, in the preparation method of the SMMA microcellular foaming material with high toughness, in step (3), the cooling time is 10 - 100 s.

[0024] During the research process, the inventors tried to introduce thermoplastic polyurethane elastomer TPU and polyolefin elastomer POE. The results showed that: Although TPU is an elastomer with relatively strong polarity and has good compatibility with SMMA after introduction, due to the poor ability of the TPU elastomer itself to cause shear yield, the cell structure of the obtained foaming material was improved to some extent, but the notched impact strength could not meet the application requirements; while POE, as a polyolefin elastomer, has good toughness, but due to its poor compatibility with SMMA, the impact strength of the prepared foaming material was not improved.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] 1. Through a large number of experiments, the inventors unexpectedly found that the SMMA microcellular foaming material obtained by physical foaming at a low air pressure of 4 - 10 MPa after co - extrusion of SBS elastomer and SMMA simultaneously has high toughness and excellent cell structure, and the notched impact strength is 2 KJ / m 2Above, the elongation at break is greater than 2.5%, the weight loss rate is above 25%, the average cell size is less than 40 microns, and the cell density is greater than 10 7 cells / cm 3 , the introduction of SBS significantly improves the toughness and cell structure of the material. The cell size of the foamed material is further reduced, and the cell density is further increased.

[0027] 2. The inventors further found through research that when a certain amount of nucleating agent is added while introducing the SBS elastomer, the cell structure can be further improved, the cell size can be reduced, and the cell density can be increased. Description of the Drawings

[0028] Figure 1 It is a statistical chart of the cell structures of Examples 1-4 and Comparative Example 1.

[0029] Figure 2 It is a scanning electron microscope (SEM) photograph of the cell structures of Examples 1-4 and Comparative Example 1. Detailed Embodiments

[0030] The present invention will be further described below in conjunction with the drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0031] For the operation methods without specific conditions indicated in the following examples, they are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer.

[0032] Unless otherwise specified, the parts in the following examples and comparative examples all refer to parts by mass.

[0033] Example 1

[0034] Preparation of 90 parts of SMMA blended with 10 parts of SBS, i.e., 90SMMA / 10SBS foam material.

[0035] 90 parts of SMMA and 10 parts of SBS are blended through a twin-screw extruder, and the extrusion speed is 60 rpm, and the temperature is 160 - 230 °C.

[0036] The extruded blend is placed in an oven at 80 °C and dried for 8 hours.

[0037] The dried material is added to the barrel of an injection molding machine. The gas injection pressure is set to 8 MPa, the foaming gas is nitrogen, the material storage speed is set to 20 rpm, the holding pressure time is 2 s, and the holding pressure is 60 MPa.

[0038] Pre-plasticize the material to obtain a uniform polymer / gas melt, and inject the melt into the mold cavity at a speed of 100 mm / s and an injection pressure of 100 MPa. After holding pressure for 2 s, open the mold by 1 mm and cool for 20 s to obtain a 90SMMA / 10SBS foam material with a 25% weight reduction.

[0039] Analyze and characterize its properties. The notched impact strength is 2.82 KJ / m 2 , and the elongation at break is 2.6%, as shown in Figure 1 Sample B in Figure 2 b. The average cell size is 35 microns, and the cell density is 1.75*10 7 cells / cm 3 .

[0040] Example 2

[0041] Preparation of 70 parts of SMMA blended with 30 parts of SBS, i.e., 70SMMA / 30SBS foam material.

[0042] Blend 70 parts of SMMA and 30 parts of SBS through a twin-screw extruder with an extrusion speed of 60 rpm and a temperature of 160 - 230 °C.

[0043] Place the extruded blend in an oven at 80 °C and dry for 8 hours.

[0044] Add the dried material to the injection molding machine barrel, set the gas injection pressure to 8 MPa, select nitrogen as the foaming gas, set the charging speed to 20 rpm, hold pressure for 2 s, and hold pressure at 60 MPa.

[0045] Pre-plasticize the material to obtain a uniform polymer / gas melt, and inject the melt into the mold cavity at a speed of 100 mm / s and an injection pressure of 100 MPa. After holding pressure for 2 s, open the mold by 1 mm and cool for 20 s to obtain a 70SMMA / 30SBS foam material with a 25% weight reduction.

[0046] Analyze and characterize its properties. The notched impact strength is 4.3 KJ / m 2 , and the elongation at break is 11%, as shown in Figure 1 Sample C in Figure 2 c. The average cell size is 31 microns, and the cell density is 1.99*10 7 cells / cm 3 .

[0047] Compared with Example 1, the proportion of SBS in Example 2 increases, the melt strength improves, and the cell structure is significantly improved. Due to the improvement of the cell structure and the increase in the elastomer content, its notched impact strength is significantly improved, and the elongation at break is significantly improved.

[0048] Example 3

[0049] Preparation of 70 parts of SMMA blended with 30 parts of SBS and 1 part of talc (Talc), i.e., 70SMMA / 30SBS / 1Talc foam material.

[0050] 70 parts of SMMA, 30 parts of SBS and 1 part of Talc were blended by a twin-screw extruder at an extrusion speed of 60 rpm and a temperature of 160 - 230 °C.

[0051] The extruded blend was dried in an oven at 80 °C for 8 hours.

[0052] The dried material was added to the barrel of an injection molding machine. The gas injection pressure was set at 8 MPa, nitrogen was selected as the foaming gas, the material storage speed was set at 20 rpm, the holding pressure time was 2 s, and the holding pressure was 60 MPa.

[0053] The material was pre-plasticized to obtain a uniform polymer / gas melt, and the melt was injected into the mold cavity at a speed of 100 mm / s and an injection pressure of 100 MPa. After holding pressure for 2 s, the mold was opened 1 mm and cooled for 20 s to obtain 70SMMA / 30SBS / 1Talc foam material with a weight reduction of 25%.

[0054] Its properties were analyzed and characterized. Its notched impact strength was 3.82 KJ / m 2 , and the elongation at break was 11%, as shown in sample D in Figure 1 , and as shown in d, the average cell size was 27 microns and the cell density was 2.34×10 Figure 2 cells / cm 7 3 .

[0055] Compared with Example 1, in Example 3, due to the improvement of the melt strength and the introduction of heterogeneous nucleation sites by adding talc, the cell structure of Example 3 was significantly improved. Due to the improvement of the cell structure and the increase in the elastomer content, its notched impact strength and elongation at break were significantly improved compared with Example 1. However, due to the rigid particles of talc, the notched impact strength decreased compared with Example 2. The heterogeneous nucleation of talc and the fact that talc, as an inorganic particle, increased the entanglement of polymer molecular chains, resulting in a decrease in the average cell size and an increase in the cell density compared with Example 2.

[0056] Example 4

[0057] Preparation of 60 parts of SMMA blended with 40 parts of SBS, i.e., 60SMMA / 40SBS foam material.

[0058] 60 parts of SMMA and 40 parts of SBS were blended by a twin-screw extruder at an extrusion speed of 60 rpm and a temperature of 160 - 230 °C. ​

[0059] The extruded blend was dried in an oven at 80 °C for 8 hours.

[0060] The dried material was added to the barrel of an injection molding machine. The gas injection pressure was set at 8 MPa, nitrogen was selected as the foaming gas, the screw speed was set at 20 rpm, the holding time was 2 s, and the holding pressure was 60 MPa.

[0061] The material was pre-plasticized to obtain a uniform polymer / gas melt, and the melt was injected into the mold cavity at a speed of 100 mm / s and an injection pressure of 100 MPa. After holding pressure for 2 s, the mold was opened 1 mm and cooled for 20 s to obtain a 60SMMA / 40SBS foam material with a 25% weight reduction.

[0062] Its properties were analyzed and characterized. Its notched impact strength was 8.77 KJ / m 2 , and the elongation at break was 26%, as Figure 1 in sample E, Figure 2 as shown in e, the average cell size was 26 microns, and the cell density was 2.88×10 7 cells / cm 3 .

[0063] Compared with Example 2, the proportion of SBS in Example 4 was further increased, and the melt strength was further improved, resulting in a significant improvement in the cell structure of Example 4. Due to the improvement of the cell structure and the increase in the elastomer content, its notched impact strength and elongation at break were significantly improved compared with Example 2.

[0064] Comparative Example 1

[0065] Properties and preparation method of pure SMMA foam material.

[0066] The pure SMMA foam material was dried in an oven at 80 °C for 8 h.

[0067] The dried material was added to the barrel of an injection molding machine. The gas injection pressure was set at 8 MPa, nitrogen was selected as the foaming gas, the screw speed was set at 20 rpm, the holding time was 2 s, and the holding pressure was 60 MPa.

[0068] The material was pre-plasticized to obtain a uniform polymer / gas melt, and the melt was injected into the mold cavity at a speed of 100 mm / s and an injection pressure of 100 MPa. After holding pressure for 2 s, the mold was opened 1 mm and cooled for 20 s to obtain an SMMA foam material with a 25% weight reduction.

[0069] Its properties were analyzed and characterized. Its notched impact strength was 1.33 KJ / m 2 , and the elongation at break was 2.5%, as Figure 1 in sample A, Figure 2 as shown in a, the average cell size was 40 microns, and the cell density was 107 pcs / cm 3 。

[0070] Comparative Example 2

[0071] Preparation of 60 parts of SMMA blended with 40 parts of TPU, i.e., 60SMMA / 40TPU foam material.

[0072] Blend 60 parts of SMMA and 40 parts of TPU through a twin-screw extruder, with an extrusion speed of 60 rpm and a temperature of 160 - 230 °C.

[0073] Place the extruded blend in an oven at 80 °C and dry for 8 hours.

[0074] Add the dried material to the injection molding machine barrel, set the gas injection pressure to 8 MPa, select nitrogen as the foaming gas, set the material storage speed to 20 rpm, the holding time to 2 s, and the holding pressure to 60 MPa.

[0075] Pre-plasticize the material to obtain a uniform polymer / gas melt, and inject the melt into the mold cavity at a speed of 100 mm / s and an injection pressure of 100 MPa. After holding pressure for 2 s, open the mold by 1 mm and cool for 20 s to obtain an SMMA foam material with a 25% weight reduction.

[0076] Analyze and characterize its properties. Its notched impact strength is 1.3 KJ / m 2 , the elongation at break is 2%, the average cell size is 30 microns, and the cell density is 10 7 pcs / cm 3 。

[0077] Comparative Example 3

[0078] Preparation of 60 parts of SMMA blended with 40 parts of POE, i.e., 60SMMA / 40POE foam material.

[0079] Blend 60 parts of SMMA and 40 parts of POE through a twin-screw extruder, with an extrusion speed of 60 rpm and a temperature of 160 - 230 °C.

[0080] Place the extruded blend in an oven at 80 °C and dry for 8 hours.

[0081] Add the dried material to the injection molding machine barrel, set the gas injection pressure to 8 MPa, select nitrogen as the foaming gas, set the material storage speed to 20 rpm, the holding time to 2 s, and the holding pressure to 60 MPa.

[0082] Pre-plasticize the material to obtain a uniform polymer / gas melt, and inject the melt into the mold cavity at a speed of 100 mm / s and an injection pressure of 100 MPa. After holding the pressure for 2 s, open the mold by 1 mm and cool for 20 s to obtain an SMMA foam material with a 25% weight reduction.

[0083] Analyze and characterize its properties. Its notch impact strength is 0.8 KJ / m 2 , the elongation at break is 1.3%, the average cell size is 35 microns, and the cell density is 10 7 cells / cm 3 .

[0084] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

Claims

1. A SMMA microcellular foaming material with high toughness, characterized in that, The notched impact strength of the SMMA microcellular foaming material with high toughness is above 2 KJ / m 2 and the elongation at break is greater than 2.5%; The weight reduction rate of the SMMA microcellular foaming material with high toughness is above 25%; The average cell size of the SMMA microcellular foaming material with high toughness is less than 40 microns, and the cell density is greater than 10 7 cells / cm 3 ; The preparation method of the SMMA microcellular foaming material with high toughness comprises the steps: (1) Mixing and extruding 60wt%-90wt% of SMMA, 10wt%-40wt% of elastomer SBS, and 0-5wt% of nucleating agent through a twin-screw extruder at 150-230 °C to obtain a composite material; (2) After drying the composite material obtained in step (1), adding it into a foam injection molding machine, with the screw temperature at 190-230 °C, the mold temperature at 40-100 °C, the material storage speed at 5-60 rpm, the foaming gas pressure at 4-10 MPa, pre-plasticizing the composite material to obtain a uniform melt of the composite material and a melt of gas, injecting it into the mold cavity under the conditions of an injection speed of 50-100 mm / s and an injection pressure of 40-100 MPa, holding the pressure at 40-100 MPa for 0.5-5 s, and then opening the mold for foaming; (3) Cooling the sample obtained by opening the mold for foaming to obtain the SMMA microcellular foaming material with high toughness.

2. The preparation method of the SMMA microcellular foaming material with high toughness according to claim 1, wherein, Comprises the steps: (1) Mixing and extruding 60wt%-90wt% of SMMA, 10wt%-40wt% of elastomer SBS, and 0-5wt% of nucleating agent through a twin-screw extruder at 150-230 °C to obtain a composite material; (2) After drying the composite material obtained in step (1), adding it into a foam injection molding machine, with the screw temperature at 190-230 °C, the mold temperature at 40-100 °C, the material storage speed at 5-60 rpm, the foaming gas pressure at 4-10 MPa, pre-plasticizing the composite material to obtain a uniform melt of the composite material and a melt of gas, injecting it into the mold cavity under the conditions of an injection speed of 50-100 mm / s and an injection pressure of 40-100 MPa, holding the pressure at 40-100 MPa for 0.5-5 s, and then opening the mold for foaming; (3) Cooling the sample obtained by opening the mold for foaming to obtain the SMMA microcellular foaming material with high toughness.

3. The preparation method according to claim 2, characterized in that, In step (1), the nucleating agent is an inorganic nucleating agent.

4. The preparation method according to claim 3, wherein, In step (1), the nucleating agent comprises at least one of talcum powder and calcium carbonate.

5. The preparation method according to claim 2, characterized in that, In step (1), the extrusion speed is 40-100 rpm.

6. The preparation method according to claim 2, characterized in that, In step (2), the drying temperature is 75-85 °C and the time is 6-8 h.

7. The preparation method according to claim 2, wherein, In step (2), the foaming gas is nitrogen or carbon dioxide.

8. The preparation method according to claim 2, characterized in that, In step (2), the mold opening distance is 1-3 mm.

9. The preparation method according to claim 2, wherein In step (3), the cooling time is 10-100 s.

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