阅读说明：本技术 一种抑音且高回弹性发泡聚丙烯珠粒及其应用 (Sound-suppression and high-resilience foamed polypropylene bead and application thereof ) 是由 熊业志 曾佳 蒋璠晖 刘缓缓 朱民 何若虚 于 2021-08-02 设计创作，主要内容包括：本发明属于发泡聚丙烯技术领域,具体涉及一种抑音且高回弹性发泡聚丙烯珠粒,包括如下质量百分比的各组分：聚丙烯68-91.4%、热塑性弹性体8-22%、高级脂肪酸0.1-2%、微晶石蜡0.1-3%、聚丙烯蜡0.3-4%、泡孔成核剂0.03-0.3%。本发明的抑音且高回弹性发泡聚丙烯珠粒,通过添加热塑性弹性体,有效的提高了物料的熔体强度和弹性；通过同时添加高级脂肪酸、微晶石蜡和聚丙烯蜡,起到有效的协同润滑作用,可长时间抑制发泡珠粒摩擦噪音的产生；高级脂肪酸与聚丙烯的相容性相对略差,形成短期的润滑效果；微晶石蜡的析出速度略慢,主要形成中长期的润滑效果；聚丙烯蜡与聚丙烯相容性优异,析出速度更慢,协助发挥长期的润滑作用。本发明超轻的发泡珠粒产品适用于泡沫颗粒填充领域。(The invention belongs to the technical field of expanded polypropylene, and particularly relates to a sound-suppressing high-resilience expanded polypropylene bead which comprises the following components in percentage by mass: 68-91.4% of polypropylene, 8-22% of thermoplastic elastomer, 0.1-2% of higher fatty acid, 0.1-3% of microcrystalline paraffin, 0.3-4% of polypropylene wax and 0.03-0.3% of foam cell nucleating agent. According to the sound-suppressing high-resilience expanded polypropylene bead, the thermoplastic elastomer is added, so that the melt strength and elasticity of the material are effectively improved; by simultaneously adding higher fatty acid, microcrystalline wax and polypropylene wax, an effective synergistic lubrication effect is achieved, and the generation of friction noise of the expanded beads can be inhibited for a long time; the compatibility of the higher fatty acid and the polypropylene is relatively slightly poor, and a short-term lubricating effect is formed; the micro-crystal paraffin is slightly slow in precipitation speed, and mainly has a medium-long term lubricating effect; the polypropylene wax has excellent compatibility with polypropylene, has slower precipitation speed, and assists in playing a role of lubricating for a long time. The ultra-light foaming bead product is suitable for the field of foam particle filling.)

1. A sound-suppressing and high-resilience expanded polypropylene bead characterized in that: the paint comprises the following components in percentage by mass:

68 to 91.4 percent of polypropylene

8 to 22 percent of thermoplastic elastomer

Higher fatty acid 0.1-2%

Microcrystalline paraffin 0.1-3%

0.3 to 4 percent of polypropylene wax

0.03-0.3% of foam cell nucleating agent.

2. The sound-suppressing and high-resilience expanded polypropylene bead as set forth in claim 1, wherein: the polypropylene is random copolymer polypropylene.

3. The sound-suppressing and high-resilience expanded polypropylene bead as set forth in claim 1, wherein: the melting point of the polypropylene is 130-147 ℃, and the melt index is 6-8g/10 min.

4. The sound-suppressing and high-resilience expanded polypropylene bead as set forth in claim 1, wherein: the thermoplastic elastomer at least comprises two components of a melt blending polymer of polypropylene/ethylene propylene diene monomer and a propylene-alpha olefin copolymer elastomer, wherein the mass ratio of the melt blending polymer to the propylene-alpha olefin copolymer elastomer is 1: 0.8-1.2.

5. The sound-suppressing and high-resilience expanded polypropylene bead as set forth in claim 4, wherein: the melting point of the melt blending polymer is 130-145 ℃, the melt index is 1-8g/10min, the mass percent of the ethylene propylene diene monomer is 30-70%, and the mass percent of the substance insoluble in hot xylene is 15-50%;

the propylene-alpha olefin copolymer elastomer is a random copolymer of propylene-alpha olefin or a block copolymer of propylene-alpha olefin, and the mass percent of the alpha olefin in the copolymer is 3-20%;

the propylene-alpha olefin copolymer elastomer has a melting point of 115-135 ℃ and a melt index of 3-8g/10 min.

6. The sound-suppressing and high-resilience expanded polypropylene bead as set forth in claim 1, wherein: in the chemical molecular structure of the higher fatty acid, the number of carbon atoms is 10-24; the melting point of the microcrystalline paraffin is 80-90 ℃; the molecular weight of the polypropylene wax is 1500-10000.

7. The sound-suppressing and high-resilience expanded polypropylene bead as set forth in claim 1, wherein: the higher fatty acid is one or two of stearic acid and oleic acid; the foam cell nucleating agent is one or more of silicon dioxide, zinc borate, talcum powder, barium sulfate and calcium carbonate.

8. The sound-suppressing and high-resilience expanded polypropylene bead as set forth in claim 1, wherein: the foam cell nucleating agent is silicon dioxide, and the particle size of the foam cell nucleating agent is 3-6 microns.

9. The sound-suppressing and high-resilience expanded polypropylene bead as set forth in claim 1, wherein: the preparation method comprises the following steps:

(1) uniformly mixing polypropylene, a thermoplastic elastomer, higher fatty acid, microcrystalline paraffin, polypropylene wax and a foam cell nucleating agent according to a certain proportion, extruding by using a double screw, and granulating by using underwater granulating equipment to prepare spherical or ellipsoidal particles, wherein the weight of each particle is 2-5 mg;

(2) adding the particles, dispersant, surfactant and dispersing medium into autoclave, sealing, and introducing CO₂Stirring continuously to form a dispersion system; maintaining at 135-155 deg.C and 2.9-4.2MPa for 5-30min to allow blowing agent gas to be impregnated into the softened resin particles, releasing pressure to discharge the material to atmospheric pressure to obtain expanded primary expanded beads with bulk density of 35-43 g/L;

(3) and (3) sealing the primary expanded beads into a pre-pressing tank after the primary expanded beads are subjected to normal-temperature curing for 12-24h, carrying pressure by using air, wherein the pressure carrying pressure is 0.5-0.8MPa, the pressure carrying time is 12-30h, and the loaded primary expanded beads are heated and expanded at 90-107 ℃ in a normal-pressure flow-through foaming pipeline to form secondary expanded beads with lighter density, and the bulk density is 10-15 g/L.

10. Use of sound-damping and high-resilience expanded polypropylene beads as claimed in any one of claims 1 to 9, wherein: for foam particle filling.

Technical Field

The invention belongs to the technical field of expanded polypropylene, and particularly relates to a sound-suppressing high-resilience expanded polypropylene bead and application thereof.

Background

Expanded polypropylene beads (EPP) and molded articles thereof have excellent mechanical properties and a remarkable weight-reduction effect, and have been widely used for packaging buffers and interior linings of automobile parts. Along with the expansion of EPP application, a plurality of application scenes with filling property gradually use EPP beads, for example, the EPP beads can be used for filling internal foams such as lazy sofas, back cushions, cushions and mattresses, the substitution of filling foams such as EPS, pearl wool and sponge can be realized, and the effect is very good. Because the particles of the EPP beads are rounded into irregular spherical shapes, they are easy to fill, and the highly closed cell structure of the pot press process is suitable for better resilience applications. On the other hand, EPP beads are semi-crystalline air/polypropylene composites with good rigidity and the bead skin is prone to "squeaking" noise during squeeze-friction sliding, a drawback that is extremely unpleasant to the end user experience of filling markets (lazy sofas, headrests, cushions, mattresses, etc.).

Chinese patents CN 110832018A and CN 110621730 a both use olefin thermoplastic elastomer materials to prepare crosslinked foamed beads, which have good resilience and are suitable for use in filling scenes, but do not emphasize the noise suppression effect of the beads; and the cross-linking agent is added in the dispersion system of the foaming process, so that the cross-linking agent in the wastewater is not easy to recover and is easy to pollute the environment. Chinese patent CN 110709454 a uses polyolefin resin, olefin elastomer, higher fatty amide, butylene copolymer polyethylene wax, vinyl copolymer and water-absorbing substance to blend and modify, and then uses kettle pressure foaming method to obtain foaming particles and in-mold forming body with excellent gloss and suppressed friction and abnormal sound; however, the expanded bead magnification of this technique is 2 to 60P, and there is no emphasis on the expression of the resilience of the expanded beads in the high magnification ultralight state, and therefore there may be a room for improvement in the resilience of the expanded beads in the ultralight state.

Therefore, in view of the application of EPP bead fillers, it is necessary to provide ultra-light expanded polypropylene beads for filling, which have high resilience, high expansion ratio and excellent sound suppression effect, and are suitable for various applications requiring flexible foam filling.

Disclosure of Invention

In order to solve the problems, the invention discloses a sound-suppressing and high-resilience expanded polypropylene bead and application thereof.

In order to achieve the purpose, the invention adopts the following technical scheme:

a sound-suppressing and high-resilience expanded polypropylene bead comprises the following components in percentage by mass:

preferably, the polypropylene is a random copolymer polypropylene.

Preferably, the polypropylene has a melting point of 130-147 ℃ and a melt index of 6-8g/10 min.

Preferably, the thermoplastic elastomer at least comprises two components of a melt blending polymer of polypropylene/ethylene propylene diene monomer and a propylene-alpha olefin copolymer elastomer, wherein the weight ratio of the melt blending polymer to the propylene-alpha olefin copolymer elastomer is 1: 0.8-1.2.

Preferably, the melting point of the melt blending polymer is 130-145 ℃, the melt index is 1-8g/10min, the mass percent of the ethylene propylene diene rubber is 30-70%, and the mass percent of the substance insoluble in hot xylene is 15-50%;

the propylene-alpha olefin copolymer elastomer is a random copolymer of propylene-alpha olefin or a block copolymer of propylene-alpha olefin, and the mass percent of the alpha olefin in the copolymer is 3-20%;

the propylene-alpha olefin copolymer elastomer has a melting point of 115-135 ℃ and a melt index of 3-8g/10 min.

Preferably, the higher fatty acid has a chemical molecular structure in which the number of carbon atoms is 10 to 24; the melting point of the microcrystalline paraffin is 80-90 ℃; the molecular weight of the polypropylene wax is 1500-10000.

Preferably, the higher fatty acid is one or both of stearic acid and oleic acid; the foam cell nucleating agent is one or more of silicon dioxide, zinc borate, talcum powder, barium sulfate and calcium carbonate.

Preferably, the above-mentioned foam cell nucleating agent is silica, and the particle diameter of the foam cell nucleating agent is 3 to 6 μm.

Preferably, the sound-suppressing and high-resilience expanded polypropylene beads are prepared by the following method:

(1) uniformly mixing polypropylene, a thermoplastic elastomer, higher fatty acid, microcrystalline paraffin, polypropylene wax and a foam cell nucleating agent according to a certain proportion, extruding by using a double screw, and granulating by using underwater granulating equipment to prepare spherical or ellipsoidal particles, wherein the weight of each particle is 2-5 mg;

(2) adding the fine particles, dispersant (preferably kaolin), surfactant (preferably sodium dodecyl benzene sulfonate) and dispersing medium (preferably deionized water) into autoclave, sealing, and introducing CO₂Continuously stirring to form a dispersion system, namely, the particles are dispersed in the deionized water in a single particle mode under the action of a dispersing agent and a surfactant; maintaining at 135-155 deg.C and 2.9-4.2MPa for 5-30min to allow blowing agent gas to be impregnated into the softened resin particles, and releasing pressure to discharge the materialObtaining expanded primary expanded beads at atmospheric pressure, the bulk density of which is 35-43 g/L;

(3) and (3) sealing the primary expanded beads into a pre-pressing tank after the primary expanded beads are subjected to normal-temperature curing for 12-24h, carrying pressure by using air, wherein the pressure carrying pressure is 0.5-0.8MPa, the pressure carrying time is 12-30h, and the loaded primary expanded beads are heated and expanded at 90-107 ℃ in a normal-pressure flow-through foaming pipeline to form secondary expanded beads with lighter density, and the bulk density is 10-15 g/L.

The invention has the following beneficial effects:

(1) according to the sound-suppressing high-resilience expanded polypropylene bead, the thermoplastic elastomer is added, so that the melt strength and elasticity of materials are effectively improved, and a closed-cell structure and high resilience of the expanded bead under a high foaming ratio are facilitated; by simultaneously adding the higher fatty acid, the microcrystalline paraffin and the polypropylene wax, an effective synergistic lubrication effect is achieved, and the generation of friction noise of the foaming beads can be effectively inhibited for a long time; the compatibility of the higher fatty acid and the polypropylene is relatively slightly poor, and the higher fatty acid is more easily separated out to the surface of the expanded bead to form a short-term lubricating effect; the micro-crystal paraffin is slightly slow in precipitation speed, and mainly has a medium-long term lubricating effect; the polypropylene wax has higher molecular weight, excellent compatibility with polypropylene and slower precipitation speed, helps to play a long-term lubricating role and inhibits the friction noise of the expanded beads.

(2) The higher fatty acid, the microcrystalline wax and the polypropylene wax are added in relatively low amounts, so that the effect of suppressing friction noise is not easily realized, and when the corresponding addition amount is relatively high, the melt strength of the material is easily reduced, the closed cell structure of the expanded beads at a high magnification is easily damaged, and the rebound resilience is poor.

(3) The thermoplastic elastomer comprises a polypropylene/ethylene propylene diene monomer melt blending polymer of a cross-linked rubber part and a propylene-alpha olefin copolymer elastomer with excellent resilience, the melt strength of the material can be increased by simply adding a proper amount of the polypropylene/ethylene propylene diene monomer melt blending polymer, but the elasticity of the material is possibly not enough, and if the polypropylene/ethylene propylene diene monomer melt blending polymer is excessively added, the melt strength is too high, so that the high-rate foaming process is not favorable; the elasticity of the material can be effectively improved by simply adding more propylene-alpha olefin copolymer elastomer, but the melt strength can not be enhanced and the material can be softer, so that the polypropylene/ethylene propylene diene monomer melt blending polymer added with the crosslinking rubber part and the propylene-alpha olefin copolymer elastomer with excellent resilience are selected.

(4) When the single weight of the particles is less than 2mg, the number of the particles of the expanded beads required by the expanded beads in filling application with the same volume is larger, the larger the surface area of the mutual contact among the beads is, noise tends to be generated more easily when the beads are subjected to extrusion friction, the lower the transmission efficiency of force among the beads is, and the poorer the rebound effect of filling application of the piled beads is; the weight of the particles is preferably 2 to 5mg per particle, since the blowing agent may be less likely to be impregnated into the particles during the tank foaming process or the required production cycle time per tank may be longer.

(5) The particles are preferably granulated underwater, and the particles are similar to spheres or ellipsoids, so that the shapes of the particles are ensured, the corresponding expanded beads are also more similar to spheres, and the expanded beads in a stacked state have better resilience.

(6) The adoption of the optimized primary foaming process, density control and corresponding secondary foaming conditions is favorable for producing the ultralight foaming beads with the bulk density of 10-15g/L, better preserving the closed cell structure and favorable for filling high resilience in the using process. If the bulk density of the primary expanded beads is too low, the closed cell structure of the primary expanded beads is likely to be damaged, and the defect is amplified by the secondary expansion process, so that the rebound resilience is poor; the packing density of the primary expanded beads is too high, and the ultra-light expanded beads are not easy to obtain in the secondary expansion process.

Detailed Description

The present invention will now be described in further detail with reference to examples.

The main experimental material properties are shown in table 1.

TABLE 1

The higher fatty acid is stearic acid.

The formulations and parameters of examples 1-5 and comparative examples 1-8 are shown in Table 2.

TABLE 2

Table 2 the amounts of each component in the microparticle formulations of examples 1 to 5 and comparative examples 1 to 8 were in mass%.

The secondary expanded beads prepared in examples 1 to 5 and comparative examples 1 to 8 were subjected to performance tests, and the test results are shown in Table 3.

TABLE 3

The sound suppression test method comprises the following steps: the tool for testing the sound suppression effect is a pair of upper and lower metal flat plate devices which can slide relatively; the upper and lower metal plates have the length of 100mm, the width of 100mm and the thickness of 10mm, four corners of the lower surface of the lower metal plate are provided with 4 symmetrical mute movable wheels, and the lower metal plate is parallel to the experiment table; go up the metal sheet and pass through movable screw fixation on the metal pole (the metal pole is marked with the scale, and minimum precision is 1mm, and metal pole vertical fixation is on the experiment mesa), when the movable screw loosened, go up metal sheet and movable screw and all can follow the metal pole and reciprocate, adjust the position of movable screw, can adjust the distance of metal sheet from top to bottom, the metal sheet is just parallel about. Filling a polytetrafluoroethylene mesh bag (containing about 1L of material when filled with the material, and 60 meshes of meshes) with 0.6L of stacking volume of foaming beads to be tested, and sealing the mesh bag; placing the mesh bag between the upper and lower metal plates, adjusting the height of the upper metal plate to fix the metal plates at a distance of 50mm, and allowing the mesh bag containing beads to simultaneously contact the upper and lower metal plates tightly, but to be compressibleA space. The spring balance is used for repeatedly pulling the lower metal plate left and right under constant tension, beads in the mesh bag are contacted and rubbed with each other due to constant extrusion force, and whether noise is generated or not is observed. Minimal or no noise is notedThe relatively small noise is denoted "□" and the apparent "squeak" sound is denoted as

Bead filling resilience test method: testing the resilience by adopting a self-made compression mould device; the mold comprises a mold cavity and a template, wherein the mold cavity is made of metal materials, the mold cavity is in a cuboid shape without an upper bottom, the lower bottom of the mold cavity is parallel to the experiment table surface, the interior of the mold cavity comprises a cuboid-shaped cavity, the length of the cavity is 200mm, the width of the cavity is 100mm, the depth of the cavity is 100mm, 4 corners of the cavity are provided with scales in the depth direction (the scales are uniformly marked from the lower bottom to the upper bottom by 0-100 mm), and the minimum precision is 1 mm; a fixed metal column (cylindrical, 100mm in height and 10mm in diameter) with threads is arranged at each of 4 corners of the groove cavity and is vertical to the bottom of the groove, and the height of the fixed metal column is consistent with the depth of the die groove; the length of the template is 199.5mm, the width of the template is 99.5mm, the thickness of the template is 10mm, round holes (the inner diameter is 10.5mm, the depth is 10mm) are formed in four corners of the template, the template covers the upper surface of the die cavity, the positions of the holes can just correspond to cylindrical metal columns at 4 corners of the die cavity, namely the metal columns just can penetrate through the holes, and the template can directly fall to the bottom of the die cavity and is parallel to the bottom of the die cavity.

The expanded beads to be tested were loaded into the cavity and the stacked beads were loaded to be flush with the upper bottom surface of the cavity, i.e., the height of the stacked beads was 100mm before compression; then, covering the upper bottom of the die cavity by using a template, applying constant pressure to slowly press the beads downwards until the scale reading of 4 angles on the upper surface of the template corresponding to the depth direction of the die cavity is 60mm, fixing the position of the template on the metal column by using a matched nut, namely the height of the accumulated beads when being compressed is 50mm, and the template is parallel to the lower bottom of the die cavity and the experimental table top; after time t1 (2 h for each example), the 4 nuts were loosened, the template removed and the compressed packed beads began to rebound; after time t2 (0.5 h is used in the examples), the height scale value corresponding to the uppermost layer of the stacked beads (relative to the height of the threaded metal cylinder) is read at four corners of the die cavity, and the average value x is taken out, wherein the larger x (50 mm. ltoreq. x.ltoreq.100 mm) indicates the better filling resilience of the foamed beads. The above tests were carried out in a laboratory at 25 ℃ and 50% humidity.

The filling rebound rate tested on the basis is (x/100) multiplied by 100%, and the value of more than 80% in the examples is marked as 'excellent filling rebound resilience', the value of 70% -80% is marked as 'good filling rebound resilience', and the value of less than 70% is marked as 'normal filling rebound resilience'.

The thermoplastic elastomers in the comparative example 1 are all melt-blended polymers of polypropylene/ethylene propylene diene monomer, the cross-linking component of the thermoplastic elastomers has great influence on the melt strength of the material, the expansibility of the material is inhibited, the secondary foaming bead bulk density is reduced to 15g/L by forcibly adjusting the foaming parameters, the closed cell structure is possibly damaged, and the filling resilience is reduced. The thermoplastic elastomers in comparative example 2 are all propylene-alpha olefin copolymer elastomers, which may weaken the melt strength of the material during foaming to some extent, the closed cell structure of the expanded beads is also affected, and the filling resilience of the secondary expanded beads is reduced. Comparative example 3 lacks the lubricating contribution of stearic acid from rapid extraction, and the expanded beads are stored for a short period of time with slight frictional noise. Comparative example 4 lacks the lubricating contribution of microcrystalline wax; the stearic acid can be separated out and lubricated in a short time, so that the noise can be effectively inhibited; the expanded beads were stored for more than 90 days, the amount of stearic acid precipitated was reduced, and the polypropylene wax was not precipitated yet, so that slight noise was generated; with the longer the storage time is, the polypropylene wax begins to be primarily precipitated, and the noise suppression effect becomes good. Comparative example 5 lacks the lubricating contribution of the polypropylene wax; the foam beads are stored for 180 days, and the stearic acid and the microcrystalline paraffin are gradually separated out and lubricated, so that the noise can be effectively inhibited; the expanded beads were stored for more than 360 days, and the amount of stearic acid and microcrystalline wax precipitated was reduced, so that slight noise was generated. Comparative example 6 lacks the lubricating contribution; the expanded beads always show a large frictional noise. Comparative example 7 because the fine particles are light in weight per unit, the expanded beads of the same magnification are small in volume per unit, the number of the expanded beads in the filling test (same packing volume) of the same volume is large, the contact surface between the beads is large during the rebound test, the rebound force of conduction between the beads is easily lost, and the filling rebound rate is reduced.

In light of the foregoing description of the preferred embodiment of the present invention, many modifications and variations will be apparent to those skilled in the art without departing from the spirit and scope of the invention. The technical scope of the present invention is not limited to the content of the specification, and must be determined according to the scope of the claims.