BR-112021004036-B1 - METHOD FOR PRODUCING AN EXPANDED POLYAMIDE RESIN BEAD

BR112021004036B1BR 112021004036 B1BR112021004036 B1BR 112021004036B1BR-112021004036-B1

Abstract

"POLYAMIDE RESIN FOAM PARTICLES AND METHOD FOR PRODUCING THEM". The present invention relates to polyamide resin foam particles comprising a foam layer obtained by foaming a polyamide resin, wherein a first DSC curve between a first DSC curve and a second DSC curve includes: a melting peak (characteristic peak) having a maximum temperature on a low-temperature side less than or equal to the maximum temperature of the melting peak of the second DSC curve; and a melting peak (high-temperature peak) having a maximum temperature on a high-temperature side higher than the maximum temperature of the second DSC curve. The maximum temperature of the melting peak of the second DSC curve is 180-280°C, the apparent density of the polyamide resin foam particles is 10-300 kg/m3, and the closed-cell ratio is 85% or more.

Inventors

Tatsuya Hayashi
Akinobu Hira

Assignees

JSP CORPORATION

Dates

Publication Date: 20260317
Application Date: 20190904
Priority Date: 20180904

Claims (3)

1. Method for producing an expanded polyamide-based resin bead, comprising a foam layer formed by expanding a polyamide-based resin having a melting point of 180°C or higher and 280°C or lower, characterized in that it comprises: a step of dispersing a polyamide-based resin bead comprising a polyamide-based resin having a melting point of 180°C or higher and 280°C or lower in water in a closed vessel to obtain a dispersion; a step of impregnating the polyamide-based resin bead in the dispersion with a blowing agent; a step of maintaining the dispersion at a temperature greater than or equal to 90°C lower (Tm - 90°C) and less than 50°C lower (Tm - 50°C) than the melting point (Tm) of the polyamide-based resin for a retention time of 1 minute or higher and 60 minutes or lower; and a step of controlling a temperature (Te) of the dispersion immediately before expansion to a temperature greater than or equal to 90°C lower (Tm - 90°C) and less than 50°C lower (Tm - 50°C) than a melting point (Tm) of the polyamide-based resin and then discharging the polyamide-based resin bead comprising the blowing agent along with water from inside the closed vessel at a pressure lower than the pressure in the closed vessel to cause expansion, wherein the expanded polyamide-based resin bead comprising a foam layer formed by expansion of a polyamide-based resin is defined by the fact that: in a first DSC curve and a second DSC curve obtained under condition 1 below, the first DSC curve has a melting peak (intrinsic peak) having a maximum temperature on a low-temperature side less than or equal to a maximum temperature of a melting peak of the second DSC curve and a melting peak (high-temperature peak) having a maximum temperature on a high-temperature side greater than high than the maximum temperature of the second DSC curve, and the maximum melting peak temperature of the second DSC curve is 180°C or more and 280°C or less, the difference between the maximum intrinsic peak temperature and the maximum high-temperature peak temperature is 10°C or more, the expanded polyamide resin bead has an apparent density of 10 to 300 kg/m3 and a closed-cell ratio of 85% or more, and the ratio of the total high-temperature peak melting heat to the total intrinsic peak melting heat and the high-temperature peak melting heat in the first DSC curve is 10% or more and 45% or less: condition 1 a DSC curve measured when a foam layer of an expanded polyamide resin bead as a test piece is heated and melted from 30°C to a temperature 30°C higher than the temperature at the end of a melting peak at A heating rate of 10°C/min is defined as a first DSC curve, and a DSC curve measured when the test piece is then held at temperature for 10 minutes, cooled to 30°C at a cooling rate of 10°C/min, and then reheated and melted to a temperature 30°C higher than the temperature at the end of the melting peak at a heating rate of 10°C/min is defined as a second DSC curve, each curve being measured by differential scanning calorimetry of the heat flow according to the JIS K7121-1987 standard.
2. Method for producing an expanded polyamide-based resin bead according to claim 1, characterized in that the blowing agent is an inorganic physical blowing agent.
3. Method for producing an expanded polyamide-based resin bead according to claim 1 or 2, characterized in that the polyamide-based resin is an end-capped polyamide-based resin that is end-capped with a carbodiimide compound.

Description

Technical Field [001] The present invention relates to an expanded polyamide-based resin bead and a method for producing them. Background of the Technique [002] Materials used in vehicle parts need to have, for example, high mechanical strength and high rigidity. Furthermore, from the point of view of reducing fuel costs, materials used in vehicle parts also need to be lightweight. To meet these demands, research is being conducted on the use of resin materials in place of metal as materials used in vehicle parts. Polyamide-based resins are known as high heat-resistant plastics, excellent in terms of abrasion resistance and chemical resistance. It is expected that an expanded molded body made by expanding polyamide-based resin will have low weight while maintaining excellent heat resistance, abrasion resistance, chemical resistance, among others, and as a result, subsequent application and development in automotive parts, electrical products, among others. For example, Patent Literature 1 describes an expanded molded body made of expanded polyamide-based resin. [003] An expanded molded body made of a polyamide-based resin can be produced by an extrusion expansion method, a mold forming method using expanded beads, among others. In recent years, in particular, there has been a demand for a method of obtaining expanded beads that can be applied in a mold forming process from which it is possible to obtain an expanded molded body having a complex three-dimensional shape coinciding with the molded part. [004] For example, Patent Literature 2 describes a method for obtaining expanded beads by impregnating solid pellets of a specific size under pressure with a gas inert to polyamide, transferring the pellets to an expansion apparatus, and then heating. Patent Literature 3 describes a method for obtaining expanded polyamide beads by opening one end of a vessel containing polyamide-based resin beads impregnated with a volatile blowing agent in a temperature range 50°C lower to 50°C higher than the melting point of the beads. The method described in Patent Literature 2 is a method whereby resin beads are impregnated with a blowing agent, and then the resin beads impregnated with the blowing agent are removed without expansion, and then heated by an expansion apparatus to obtain expanded beads. This method is known as the "impregnation expansion method". On the other hand, in the method described in Patent Literature 3, resin beads dispersed in a dispersion medium in a closed apparatus are impregnated with a blowing agent, the temperature is increased to near the softening point of the resin, and then the resin beads are discharged out of the apparatus along with the dispersion medium at low pressure to obtain expanded beads. This method is called the "direct expansion method". List of References Patent Literature [005] PTL 1: WO 2016/147582 [006] PTL 2: JP 2011-105879 A [007] PTL 3: JP 61-268737 A Summary of the Invention Technical Problem [008] The expanded molded body of polyamide-based resin described in Patent Literature 1 has insufficient compressive strength at high temperature. [009] Therefore, initially, a problem to be solved by the present invention (first object) is to present an expanded polyamide-based resin bead having excellent high-temperature compression resistance and excellent mold conformability. [010] Furthermore, in the method described in Patent Literature 2, it is necessary to heat to a high temperature that is greater than or equal to the melting point of the polyamide-based resin to expand the composite pellets of the polyamide-based resin to obtain an expanded bead. Polyamide-based resins generally have a high melting point and are difficult to expand by heating with water vapor or similar methods using water vapor at atmospheric pressure. It is necessary to expand polyamide-based resins using hot air as a heat source. However, since hot air is a gas, there are problems such as the difficulty in controlling the temperature and the difficulty in uniformly heating a polyamide-based resin having a high melting point to a high temperature. Furthermore, when a polyamide-based resin having a high melting point is expanded at atmospheric pressure, special equipment that can be heated to high temperatures is required, and thus there is also the problem of increased investment costs. [011] In the method described in Patent Literature 3, there is the problem that in order to obtain expanded polyamide-based resin beads, the temperature at the time of expansion needs to be set within a relatively high temperature range of 50°C lower to 50°C higher than the melting point of the polyamide-based resin beads, otherwise it is not possible to obtain the expanded polyamide beads. [012] Thus, a second problem to be solved by the present invention (second object) is to present a method for producing an expanded polyamide-based resin bead capable of forming the polyamide-based resin bead at a temperature greate