CN102070841B - Polypropylene foam sheet prepared from composite foaming agent and production method thereof - Google Patents

Abstract

The invention relates to a polypropylene foam sheet using a composite foaming agent and a production method thereof. The present invention firstly provides a polypropylene foam sheet, which has the following raw material composition: polypropylene resin, 100 parts by weight; nucleating agent, 0.1-3 parts by weight; antioxidant, 0.1-3 parts by weight; cell stability agent, 0.1-3 parts by weight; composite blowing agent; wherein, the composite blowing agent includes 1-10 parts by weight of the first component blowing agent and 0.5-5 parts by weight of the second component blowing agent. The present invention also provides a production method of the above-mentioned polypropylene foam sheet. The polypropylene foam sheet provided by the present invention is a kind of polypropylene foam sheet with medium and low expansion ratio, and the product has excellent expansion ratio, cell size distribution and comprehensive evaluation of mechanical properties, and is suitable for rigid load bearing and thermal insulation. Molded. The production process of the preparation method of the polypropylene foam sheet provided by the invention is highly continuous and stable, the production process is safe and has no environmental pollution, and is suitable for industrial scale production.

Description

Polypropylene foam sheet using composite blowing agent and production method thereof

technical field

The invention relates to a polypropylene foam sheet using a composite foaming agent and a production method thereof, belonging to the technical field of polymer foam material preparation.

Background technique

Polymer foam sheet has been widely used in various industries and daily life due to its light weight, heat insulation, sound insulation, energy absorption, cushioning and other advantages. According to the expansion ratio of the polymer foam material, that is, the ratio of the density of the polymer matrix resin to the density of the foam material, the polymer foam material can be divided into ultra-high ratio (more than 40 times), high ratio (40-4 times) and low magnification (below 4x). Among them, the low-magnification polymer foam sheet not only has the general characteristics of foam sheets, but also has good rigidity and heat resistance, and is very suitable for applications such as cups, bowls and other containers that require sufficient rigidity materials etc.

But some applications require high heat resistance of the foam sheet, and the heat resistance of common polyethylene, polystyrene and polyurethane foams is not high enough. In addition, polystyrene and polyurethane foam products are not easily recyclable after their useful life, while polyethylene foam is generally not sufficiently rigid.

Polypropylene (PP) resin has good rigidity, high heat deflection temperature, chemical resistance and easy recycling, which is very suitable as a matrix resin for foam sheet. Polypropylene foam sheets with certain heat resistance and rigidity can be obtained after compression molding using expandable polypropylene beads, but in some cases this polypropylene foam sheet may not have a high enough tensile strength Mechanical properties such as strength, impact strength and bending strength.

Chinese patent CN1271125C discloses a polypropylene foaming method, which is to disperse polypropylene resin particles in an autoclave containing a dispersion medium of an organic peroxide, and then heat the dispersion to decompose the organic peroxide to thereby The process of surface-modifying polypropylene resin particles and using a foaming agent to obtain polypropylene foam beads from the non-crosslinked, surface-modified polypropylene resin particles after the autoclave is released. However, this process has a long production cycle, complex process and high cost.

In the 1990s, with the introduction of high melt strength polypropylene by Basell and Borealis, a major breakthrough was made in the continuous production of polypropylene foam. U.S. Patent No. 6,251,319 discloses a method of using butane as a foaming agent to prepare polypropylene foam sheets. However, butane is an inflammable and explosive gas that requires special handling during use and production. Therefore, the polypropylene The cost of foam board is higher.

Chinese patent CN1118507C discloses a method for manufacturing a thermoformable polypropylene foam sheet. This method uses high-melt-strength polypropylene, but the porosity of the product can reach up to 70% and the cell size is relatively large, which is not conducive to rigid load bearing in some occasions.

Chinese patent CN1435315A discloses a foamed polypropylene resin sheet containing a foamed layer, and the sheet produced by this method also contains a resin skin layer of a solid layer accounting for 20% of the total thickness. However, the production process of this method is complicated, and specially designed runners and dies are needed to realize the rapid and firm bonding of the solid layer and the foamed layer, and the requirements for equipment and operation level are relatively high.

Chinese patent CN101538387A discloses a polypropylene foam material and its production method. The method uses supercritical fluid as a foaming agent. Since the state of supercritical fluid is unstable, it is difficult to use for transportation and metering, so the extrusion foaming process is not enough Stable, it is difficult to guarantee large-scale production.

Therefore, it is one of the problems to be solved urgently in this field to find a new type of polypropylene foam material to adapt to continuous and stable large-scale production.

Contents of the invention

In order to solve the above-mentioned technical problems, the object of the present invention is to provide a polypropylene foam sheet and its production method which adopt composite blowing agent technology, have medium and low expansion ratio, have good rigidity and are suitable for continuous scale production.

To achieve the above object, the present invention at first provides a kind of polypropylene foam sheet, and it has following raw material composition:

Polypropylene resin, 100 parts by weight; nucleating agent, 0.1-3 parts by weight; antioxidant, 0.1-3 parts by weight; cell stabilizer, 0.1-3 parts by weight; composite foaming agent;

Wherein, the composite foaming agent includes 1-10 parts by weight of the first component foaming agent and 0.5-5 parts by weight of the second component foaming agent.

In the above-mentioned polypropylene foam sheet, the total amount of the composite blowing agent used can be controlled to be 2-18 parts by weight (preferably 2-10 parts by weight), preferably, the first component blowing agent used can be It is liquid carbon dioxide etc.; The second component blowing agent that adopts can be the mixture of one or more in azo compound, sulfonyl hydrazide compound and citric acid etc., or can be the mixture that contains above-mentioned blowing agent (namely azo Compound, sulfonyl hydrazide compound and citric acid, etc.) in the mixture of one or several polymer masterbatches. More preferably, the above-mentioned second component foaming agent can be a mixture of one or more of azodicarbonamide, 4,4-disulfonylhydrazide diphenyl ether and citric acid, or a mixture containing the above-mentioned foaming agent A mixture of one or several polymer masterbatches in the agent.

Among the composite foaming agents mentioned above, the first component of the foaming agent is the main foaming agent used for foaming polypropylene, and the second component of the foaming agent can increase the cell density. In addition to the above-mentioned two-part components, the composite blowing agent used in the present invention can also include a third component blowing agent of 0.5-3 parts by weight, which can improve the cell size The effect, and the third component blowing agent can be one or a mixture of water, ethanol, butane, pentane, methyl formate and dimethyl ether, etc.

In the polypropylene foam sheet provided by the present invention, preferably, the melt flow rate of the polypropylene resin is 2-5g/10min, and the polypropylene resin can be high melt strength polypropylene or high melt strength polypropylene A mixture of propylene and general-purpose polypropylene, and when a mixture of high-melt strength polypropylene and general-purpose polypropylene is used, the weight ratio of the two is 90:10 to 50:50. Among them, the general-purpose polypropylene used may preferably be isotactic polypropylene, random copolymerized polypropylene, block polypropylene, and the like.

In the polypropylene foam sheet provided by the present invention, the nucleating agent is mainly used to increase the cell density, and its mechanism of action is different from that of the second component foaming agent. Preferably, the nucleating agent used can be talcum powder, One or a mixture of calcium carbonate, nano-montmorillonite, titanium dioxide and silicon dioxide.

In the polypropylene foam sheet provided by the present invention, the antioxidant is mainly used to prevent the β degradation of polypropylene when it is heated during processing. Preferably, the antioxidant used can be tetrakis (3,5-di-tert-butyl Base-4-hydroxy)phenylpropionate pentaerythritol, tris(2,4-di-tert-butylphenyl)phosphite and β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate One or more mixtures of hydroxyaromatic compounds such as octa-carbon alcohol esters.

In the polypropylene foam sheet provided by the present invention, the cell stabilizer is mainly used to improve the strength of the cell wall, prevent the rupture of the cell wall, and play a role in stabilizing the cells. Preferably, the cell used The stabilizer is one or more mixtures of glycerin fatty acid ester cell stabilizer, propylene glycol fatty acid ester cell stabilizer and isooctyl fatty acid ester cell stabilizer. More preferably, the cell stabilizer used is a glycerol fatty acid ester cell stabilizer, such as glycerol monostearate, which can generally be obtained by esterification of fatty acids containing C16-C18 with glycerin, glycol, etc. A class of compounds.

The polypropylene foam sheet provided by the present invention can be prepared by using the above-mentioned raw materials through continuous extrusion foaming.

The present invention also provides the production method of above-mentioned polypropylene foam sheet, it comprises the following steps:

Uniformly mixing the polypropylene resin, the second component chemical foaming agent, nucleating agent, antioxidant and cell stabilizer to obtain a mixed material;

The mixed material is extruded and granulated on a twin-screw extruder, and dried at 75-80°C for 5-6 hours to form a foaming raw material;

Add the above-mentioned foaming raw materials into the extruder for continuous extrusion foaming, inject the first component foaming agent or the mixture of the first component foaming agent and the third component foaming agent into the extruder, and after thorough mixing and cooling , extruded and foamed to obtain a polypropylene foam sheet.

In the process of preparing polypropylene foam sheets, the extruder for continuous extrusion foaming can be a two-stage single-screw-single-screw tandem extruder, a two-stage twin-screw-single-screw tandem extruder or a single-screw extruder. Single-stage single-screw extruder, the processing temperature can be controlled at 160-230°C.

When adding the first component foaming agent or the mixture of the first component foaming agent and the third component foaming agent, it can be carried out by the equipment commonly used in extrusion foaming, preferably a high-precision foaming agent metering system can be used , which is dedicated to liquids and mainly consists of a liquid storage tank, a primary booster pump, a secondary metering pump and a metering system for mass flow control. When adding, the injection amount (injection speed) of the first component blowing agent or the mixture of the first component blowing agent and the third component blowing agent can be controlled to 0.6-6kg/h. This foaming agent metering system can ensure accurate and stable delivery and metering of the foaming agent for a long time during the production process, wherein the booster pump used can be a plunger compression pump or a diaphragm compression pump.

The die used in the extruder can be a ring or sheet die with electric heating or oil bath heating and temperature control, and a foam stabilizer for controlling the uniformity of the melt can be equipped at the rear of the die. device.

Compared with the prior art, the technical solution provided by the present invention has the following advantages:

The polypropylene foam sheet provided by the present invention is a polypropylene foam sheet with medium and low expansion ratio, and the product has excellent expansion ratio, cell size distribution and comprehensive evaluation of mechanical properties, and is suitable for rigid load bearing and thermal insulation. Molded. The production process of the preparation method of the polypropylene foam sheet provided by the invention is highly continuous and stable, the production process is safe and has no environmental pollution, and is suitable for industrial scale production.

Description of drawings

The following drawings are only intended to illustrate and explain the present invention schematically, and do not limit the scope of the present invention. in:

Fig. 1 is the scanning electron micrograph of the polypropylene foam sheet that embodiment 1 obtains;

Fig. 2 is the scanning electron micrograph of the polypropylene foam sheet that embodiment 2 obtains.

Detailed ways

In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical solutions of the present invention will be described in detail below with reference to the accompanying drawings, but this should not be construed as limiting the scope of the present invention.

The polypropylene foam sheet that adopts composite blowing agent provided by the present invention can be prepared according to the following specific production methods:

1. Uniformly mix polypropylene resin, nucleating agent, antioxidant and cell stabilizer to obtain a mixed material. The raw material composition of each embodiment is as shown in Table 1;

2. Extrude and granulate the above-mentioned mixture on a twin-screw extruder. The processing temperatures in the extruder zone 1 to zone 6 are 180°C, 190°C, 210°C, 220°C, 210°C, and 190°C. The head temperature is 180°C, and after drying at 80°C for 6 hours, a special foaming raw material is formed;

3. Add the second component foaming agent to the above raw materials, and after mixing evenly, add the special extruder for continuous extrusion foaming, and the first component foaming agent or the first component will be distributed by the high-precision foaming agent metering system. The mixture of the foaming agent and the third component foaming agent is injected into the extruder, and the extruder is fully mixed and temperature controlled. The temperature of the extruder is respectively 180, 185, and 190°C in the conveying area; 195, 200, and 195°C in the compression area. , 190, 185, 180, 175, 170°C; homogenization zone 160, 160, 160, 160°C; head temperature 158°C. It is extruded and foamed through a special die for extruding foamed sheets, and the width of the formed sheet is 400-1000mm.

The apparent density of the polypropylene foam sheet is obtained by standard testing according to the method of GB1033-86, and then the value of the expansion ratio can be calculated according to the formula "expansion ratio = polymer resin density/foam apparent density after foaming"; The polypropylene foam material was quenched with liquid nitrogen, and the section was sprayed with gold to observe the section with a scanning electron microscope (SEM). The cell size and cell density can be calculated. The specific test results are shown in Table 1.

Table 1

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the scope of the present invention. Protection scope, within the spirit and principles of the present invention, any modification, equivalent replacement, improvement, etc., shall be included in the protection scope of the present invention.

Claims (6)

1. A polypropylene foam sheet, which has the following raw material composition: Polypropylene resin, 100 parts by weight; nucleating agent, 0.1-3 parts by weight; antioxidant, 0.1-3 parts by weight; cell stabilizer, 0.1-3 parts by weight; composite foaming agent; Wherein, the composite blowing agent includes 1-10 parts by weight of the first component blowing agent and 0.5-5 parts by weight of the second component blowing agent; wherein, the first component blowing agent is liquid carbon dioxide; The second component foaming agent is a mixture of one or more of azo compounds, sulfonyl hydrazide compounds and citric acid, or the second component foaming agent is a mixture containing azo compounds, sulfonyl hydrazide compounds A mixture of one or several polymer masterbatches in citric acid; The composite blowing agent also includes a third component blowing agent of 0.5-3 parts by weight, and the third component blowing agent is water, ethanol, butane, pentane, methyl formate and dimethyl ether one or a mixture of several; And, the production method of this polypropylene foam sheet comprises the following steps: Uniformly mixing polypropylene resin, nucleating agent, antioxidant and cell stabilizer to obtain a mixed material; Extrude and granulate the above-mentioned mixed materials on a twin-screw extruder. The processing temperatures of the extruder zone 1 to zone 6 are 180°C, 190°C, 210°C, 220°C, 210°C, and 190°C. It is 180°C, after drying at 80°C for 6 hours, it will form a special foaming raw material; Add the second component foaming agent to the foaming raw material, and after mixing evenly, add the extruder for continuous extrusion foaming, and use the high-precision foaming agent metering system to mix the first component foaming agent and the third group The mixture of foaming agent is poured into the extruder for continuous extrusion foaming, fully mixed and temperature controlled by the extruder, wherein the temperature of the extruder is 180, 185, 190 °C in the conveying area; 195, 200, 195 °C in the compression area , 190, 185, 180, 175, 170°C; homogenization zone 160, 160, 160, 160°C; machine head temperature 158°C; extruded and foamed through a foam sheet die to obtain the polypropylene foam sheet material. 2. polypropylene foam sheet as claimed in claim 1, wherein, said second component whipping agent is a kind of in azodicarbonamide, 4,4-disulfonyl hydrazide diphenyl ether and citric acid Or a mixture of several types, or, the second component foaming agent is a mixture of polymer masterbatches containing one or several types of the above foaming agents. 3. The polypropylene foam sheet as claimed in claim 1, wherein the nucleating agent is one or a mixture of talcum powder, calcium carbonate, nano-montmorillonite, titanium dioxide and silicon dioxide. 4. The polypropylene foam sheet as claimed in claim 1, wherein the antioxidant is tetrakis (3,5-di-tert-butyl-4-hydroxyl) pentaerythritol phenylpropionate, three (2,4- One or more mixtures of di-tert-butylphenyl) phosphite and β-(3,5-di-tert-butyl-4-hydroxyphenyl) octadecyl propionate. 5. polypropylene foam sheet as claimed in claim 1, wherein, said cell stabilizer is glycerol fatty acid ester cell stabilizer, propylene glycol fatty acid ester cell stabilizer and isooctyl alcohol fatty acid ester cell One or several mixtures of stabilizers. 6. the production method of the polypropylene foam sheet described in any one of claim 1-5, it comprises the following steps: Uniformly mixing polypropylene resin, nucleating agent, antioxidant and cell stabilizer to obtain a mixed material; The mixed material is extruded and granulated on a twin-screw extruder. The processing temperatures of the extruder zone 1 to zone 6 are 180°C, 190°C, 210°C, 220°C, 210°C, and 190°C. The temperature is 180°C, after drying at 80°C for 6 hours, a special foaming raw material is formed; Add the second component foaming agent to the foaming raw material, and after mixing evenly, add the extruder for continuous extrusion foaming, and use the high-precision foaming agent metering system to mix the first component foaming agent and the third group The mixture of foaming agent is poured into the extruder for continuous extrusion foaming, fully mixed and temperature controlled by the extruder, wherein the temperature of the extruder is 180, 185, 190 °C in the conveying area; 195, 200, 195 °C in the compression area , 190, 185, 180, 175, 170°C; homogenization zone 160, 160, 160, 160°C; machine head temperature 158°C; extruded and foamed through a foam sheet die to obtain the polypropylene foam sheet material.

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