TWI755709B - Thermoplastic material for using in supercritical fluid injection foaming - Google Patents

Abstract

Present invention is related to a thermoplastic material for using in supercritical fluid injection foaming having a thermoplastic material, a reactive modifier and a nucleator. The thermoplastic material of the present invention is suitable for using in supercritical fluid injection foaming for which it could improve the problems of the conventional chemical foaming techniques. The final product produced by the thermoplastic material of the present invention has the advantages like uniformly foaming and the foaming cells of the final product are all stated in closured without breaking. The thermoplastic material of the present invention is also recyclable for benefitting the environmental protection.

Description

A thermoplastic material that can be used for injection foaming of supercritical fluids

A thermoplastic material, particularly a thermoplastic material formulation suitable for injection foaming of supercritical fluids. In detail, it particularly relates to a thermoplastic material formulation that can be used to manufacture products with excellent cushioning, thermal insulation, insulation performance, etc., and uses supercritical fluid injection foaming technology.

Foam products are widely used in various products in daily life. Due to the different types of foam structures inside, they are endowed with a wide range of application characteristics, such as internal insulation materials, buffer materials, sound insulation materials, thermal insulation materials, food packaging materials, clothing and shoes. Materials, building materials, etc., have become one of the indispensable and important products in various fields. Among the existing foam materials, polymer foam materials account for the major part of the overall market. As of 2015 estimates, polyurethane and other petroleum product polymer foams, such as polystyrene, polypropylene and polyethylene, valued at more than $100 billion, dominated the overall market, while biopolymer-based foams, Foamed materials such as polylactic acid or other derived from naturally occurring polymers such as cellulose and starch are increasing their market penetration.

At present, foaming technology can be mainly divided into chemical foaming and physical foaming. The chemical foaming technology mainly uses chemical foaming agents, such as azo foaming agents or AC foaming agents, in the foaming formula. However, chemical foaming technology may have the problem of residual chemical foaming agent, which affects product quality or performance.

Physical foaming technology, also commonly known as supercritical fluid foaming technology, mainly foams materials through supercritical fluids, such as alkanes, carbon dioxide, hydrogen and other gases. The role of plasticizer, this foaming technology will not have the problem of foaming gas remaining in the product, and it has the advantages of lowering the injection operating temperature, lowering the injection pressure, lowering the clamping force, no pressure holding, no shrinkage problem and no cooling time. Short, can reduce the production cycle advantage. However, the problems of foaming uniformity and cell breaking of the current physical foaming technology are the keys that are technically difficult to overcome.

In view of this, there is currently a lack of a material formula that can be applied to supercritical fluid foaming technology, and that the foaming of high foaming ratio molding materials is uniform and not easy to break.

In order to solve the problems that the chemical foaming is easy to have residues that affect the product quality, and the foaming uniformity and cell breaking of the existing physical foaming technology, the present invention provides a supercritical fluid ejection A thermoplastic material formulation of a foam, comprising: a thermoplastic material; a reactive modifier; and an inorganic nucleating agent.

Wherein, the thermoplastic material comprises thermoplastic polyurethane, polyethylene terephthalate, polyester thermoplastic elastomer, polylactic acid, ethylene vinyl acetate, polyolefin or its copolymer.

Wherein, the reactive modifier includes epoxides, isocyanates, dianhydride compounds, oxazolines, carbodiimides, phosphites or organic peroxides.

Preferably, the epoxide comprises polyfunctional glycidyl ester polymers, triglycidyl isocyanurate, epoxy silanes such as 3-glycidyloxypropyltrimethoxysilane, 3-glycidyl ether Oxypropyltriethoxysilane; the isocyanates include diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, blocked dicyclohexylmethane diisocyanate, or isocyanate silanes such as 3-isocyanatopropyl triethoxysilane, 3-isocyanatopropyltrimethoxysilane; the oxazoline comprises 2,2'-bis-2-oxazoline; the carbodiimide comprises carbodiimide or polycarbodiimide; The phosphite comprises trinonylphenyl phosphite or triphenyl phosphite; and the organic peroxide comprises dicumyl peroxide, tert-butylcumene peroxide, 2,5-dimethyl- 2,5-bis(tert-butylperoxide)hexane, 1,3-bis-butylperoxy cumene or 1,1-di-tert-butylperoxy-3,3,5-trimethyl ring Hexane.

Wherein, the inorganic nucleating agent comprises white smoke, mica, talc or nanocellulose.

Preferably, the inorganic nucleating agent comprises white smoke, mica, talc or nanocellulose modified with aminosilane.

More preferably, the inorganic nucleating agent comprises at least one modified with aminosilane and one unmodified white smoke, mica, talc or nanocellulose added to the thermoplastic material formulation.

As can be seen from the above description, the present invention has the following advantages:

1. The present invention adopts physical foaming and foaming technology, in addition to improving the problem that the foaming agent of chemical foaming is easy to remain, it also achieves uniform foaming of physical foaming and unbroken cells by means of formula material modification. It is an excellent and innovative technology development that can produce high-quality products with high foaming ratio.

2. Further self-test results show that the material formula of the present invention is remeltable compared to the existing physical foam materials, and the material formula is environmentally friendly and recyclable.

In order to understand the technical features and practical effects of the present invention in detail, and to implement it according to the contents of the description, the preferred embodiments shown in the drawings are further described in detail as follows.

The invention provides a thermoplastic material formulation suitable for supercritical fluid injection foaming, which comprises 96.5-99.3 wt% of thermoplastic material, 0.2-2.0 wt% of reactive modifier and 0.5-1.5 wt% of inorganic nucleating agent.

The thermoplastic material includes thermoplastic polyurethane (Thermoplastic polyurethanes, TPU), polyethylene terephthalate (Polyethylene Terephthalate, PET), polyester thermoplastic elastomer (Thermoplastic polyether ester elastomer, TPEE), Polylactic Acid (Polylactic Acid or Polylactide, PLA), another ethylene-vinyl acetate (Ethylene-vinyl acetate, EVA), polyolefin, polyolefin copolymer.

Please refer to Table 1 below, the aforementioned reactive modifier includes Epoxy compounds, Isocyanate compounds, Dianhydride, Oxazoline, and carbodiimide. (Carbodiimide), phosphite (Phosphite) or organic peroxide (Organic peroxide).

Table 1. Reactive modifier type Epoxy compounds Polyfunctional glycidyl ester polymers (Joncryl ADR 4370, ADR-4370F, ADR-4370S ADR and ADR 4468 compounds, referred to as ADR), triglycidyl isocyanurate (Triglycidyl Isocyanurate, TGIC); epoxy silane (Epoxy silane) Silanes) such as 3-glycidyloxypropyltrimethoxysilane (A-187), 3-glycidyloxypropyltriethoxysilane (A-1871) and other compounds. Isocyanate compounds Methylenediphenyl Diisocyanate (MDI), Hexamethylene diisocyanate (HDI), Hexamethylene diisocyanate (HDI trimer) and isocyanate silane (NCO- silane) such as 3-isocyanatopropyltriethoxysilane (A-Link 25 Silane), 3-isocyanatopropyltrimethoxysilane (A-Link 35 Silane) and other compounds. Dianhydrides Any dianhydride compound can be used Oxazoline 2,2'-bis-2-oxazoline (2,2'-bis(2-oxazoline), 2,2-BOZ) Carbodiimide Carbodiimide (Carbodiimide, CDI), Polycarbodiimide (Polycarbodiimide, PCDI) Phosphite Trinonylphenyl phosphite (TNPP), triphenyl phosphite (TPP) Organic peroxide Dicumyl peroxide (DCP), tert-butyl cumyl peroxide (Tert-butyl cumyl peroxide), 2,5-dimethyl-2,5-bis(tert-butyl peroxide) hexane Alkane (2,5-dimethyl-2,5-di(tert-butyl peroxide) hexane), 1,3-bis(tert-butyl peroxy isopropyl) benzene) , 1,1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane (1,1'-bis-(tert-butyl-peroxy)-3,3,5 trimethylcyclohexane, TMCH)

Among them, the reactive modifier is mainly used to improve the melt strength of the thermoplastic material during the foaming process. In order to make the foaming process withstand tension and avoid foam breaking or cell aggregation, the material modification is based on The modifier participates in or induces the polymer chain reaction. Different types of modifiers are suitable for this thermoplastic material, for example, epoxides, isocyanates, dianhydrides, oxazolines, carbodiimides or phosphites are suitable for thermoplastic polyurethane (TPU), polyparaben Modified with ethylene phthalate (PET), thermoplastic polyester elastomer (TPEE), and polylactic acid (PLA), it can be linked or grafted with the OH group and COOH group of the above thermoplastic material through specific functional groups. In order to improve the intrinsic melt strength, the addition amount can be 0.1-2.0%, or preferably 0.2-2.0 wt%. The organic peroxide can use ethylene-vinyl acetate copolymer (EVA), polyolefin, polyolefin copolymer to open the chain and bridge between the molecules to improve the intrinsic melt strength, and the addition amount can be 0.1~1.5%, or preferably 0.2 to 2.0 wt%.

Inorganic nucleating agents include white smoke (SiO ₂ ), mica (KAl ₂ (AlSi3O ₁₀ )(OH) ₂ ), talc (Talc; Mg ₃ Si4O ₁₀ (OH) ₂ ) or nanocellulose. The inorganic nucleating agent can mainly improve the heterogeneous nucleation effect of polymer materials, so that more nucleation points can be generated during the foaming process, and the cells are uniform and fine. The material modification is introduced by inorganic nucleating agent. The types of different modifiers are shown below, and 0.2~0.6% amino silane is added to modify the white smoke. The processing conditions are 190~200 ^o C, mixing at 150 rpm for 20 minutes, the main purpose is to improve the inorganic nucleating agent and organic high Compatibility of molecular materials.

The inorganic nucleating agent applicable to the present invention preferably has the following characteristics in Table 2, and can effectively achieve the effect of uniform and fine cells.

Table 2. Physical property item white smoke talcum powder Mica powder Surface area (m ² /g) 175 5.5 10.04 Pore volume (cm³/g) 1.13 0.025 0.047 Pore size (nm) 34.5 31.0 21.6

More preferably, the inorganic nucleating agent of the present invention can be modified first and then mixed with other formulation components, which can achieve better mixing uniformity. For example, the white smoke can be modified with aminosilane, and its characteristics are shown in Table 3 below.

table 3. Physical property item White smoke (SiO ₂ )/aminosilane (NH ₂ -Silane) (wt%/wt%) 100/0 97.5/2.5 95/5 Surface area (m ² /g) 175 145 137 Pore volume (cm³/g) 1.13 0.87 0.83 Pore size (nm) 34.5 30.5 27.9

"Preferred embodiment of the present invention"

<Material formula 1> Thermoplastic material: polyester thermoplastic elastomer 96.5~99.3 wt% (TPEE); Reactive modifier: ADR, NCO-silane 0.2~2% wt%; Inorganic nucleating agent: white smoke (SiO ₂ ), white smoke (SiO ₂ )/amino silane (NH ₂ -Silane) (addition amount is 0.5~1.5%).

<Production method>

The present invention mainly adopts the supercritical fluid injection foaming process, and its steps mainly include:

Establishing a single-phase solution: During the pre-plasticizing process of the screw, nitrogen or carbon dioxide is pressurized into a supercritical fluid, then injected into the screw of the injection machine and uniformly mixed with the melt formed by the aforementioned material formula 1 to form a single-phase body.

Uniform nucleation: When the single-phase body is injected into the mold cavity, thermodynamic instability occurs due to the instantaneous drop of pressure, which causes it to rapidly form phase separation, so that the gas is precipitated from the single-phase body, and countless nucleation points are instantly formed. The dots can further become a large number of fine air bubbles to generate physical foaming.

Bubble nucleation expansion and growth: After nucleation occurs, the gas diffuses into the bubbles to grow the bubbles. At this time, pressure and temperature are the conditions for adjusting the growth of the gas chamber.

Bubble solidification: The product made with the material formulation 1 of the present invention is solidified by cooling the mold.

<Processing conditions>

Corresponding to the aforementioned manufacturing method, please refer to Table 4 for the processing conditions and parameters applied in each step.

Table 4. parameter Numerical value Processing temperature ( ^o C) ^205oC Tube pressure (Bar) 11 Screw speed (rpm) 18 Injection speed (mm/s) 90 Holding pressure (Bar) 20, 40, 80 Mold temperature ( ^o C) RT N ₂ or CO ₂ content (%) 0.5 Gas stagnation time (sec) 0 Cooldown (sec) 500~700

Next, the present invention uses the above-mentioned preferred embodiment to test the validity.

Please refer to Table 5 below and Figures 1a to 1c. From this test result, it can be seen that after TPEE is modified by ADR or NCO-silane, due to the improvement of melt strength, the foaming density of the two is lower, and it can be used as a foamed product with high foaming ratio. Test items TPEE - ADR 0.5% ADR 1.0% NCO-silane 0.5% NCO-silane 1.0% Gas content (%) 1.0 1.0 1.0 1.0 1.0 Cell size (μm) 367±70 251±29 260±39 270±126 247±53 Hardness (share C) 48±1 55±1 54±1 57±1 56±1 Density (g/cm ³ ) 0.34 0.29 0.24 0.28 0.25 SEM Figure 1a -- Figure 1b -- Figure 1c

Please refer to Table 6, Table 7 and Figures 2a to 2c below. After the modified TPEE is introduced into the inorganic nucleating agent, the foamed cells are remarkably uniform, and even in the state of high foaming ratio, there is still no bubble breakage. , The products are of good quality.

Table 6. Test items TPEE ADR 1.0% - SiO ₂ 1.0% SiO ₂ /NH ₂ -Silane 1.0% Gas content (%) 1.0 1.0 1.0 Cell size (μm) 260±39 380±82 201±39 Hardness (Share C) 54±1 56±1 56±1 Density (g/cm ³ ) 0.24 0.26 0.25 SEM Figure 2a Figure 2b Figure 2c

Table 7. Test items TPEE NCO-silane 1.0% - SiO ₂ 1.0% SiO ₂ /NH ₂ -Silane 1.0% Gas content (%) 1.0 1.0 1.0 Cell size (μm) 247±53 370±126 190±53 Hardness (share C) 56±1 57±1 56±1 Density (g/cm ³ ) 0.25 0.28 0.27

Please refer to Tables 8 and 9 below. Another feature of the material formula provided by the present invention is recyclability. Generally, the addition of bridging agents in foamed products results in poor or even difficult recycling. However, the material formula provided by the present invention has Reheatable and fusible to achieve the effect of recyclability.

Table 8. Test items TPEE ADR 1.0% - SiO ₂ 1.0% SiO2/ _NH2 -Silane 1.0% Hardness (shore A) 88A 88A 88A Tm ( ^oC ) 161.9 167.9 165.2 MI (g/10 min) (200℃, 2.16 kg) 15.2 5.5 2.3 Tensile strength (kgf/cm ² ) 151.8 155.5 154.2 Elongation (%) 1521.1 1100.1 995.5

Table 9. Test items r-TPEE (recycled TPEE) ADR 1.0% - SiO ₂ 1.0% SiO ₂ /NH ₂ -Silane 1.0% Hardness (Shore A) 88A 88A 88A Tm ( ^oC ) 165.9 167.1 167.2 MI (g/10 min) (200℃, 2.16 kg) 16.2 6.2 3.2 Tensile strength (kgf/cm ² ) 150.8 150.5 154.2 Elongation (%) 1521.1 990.1 982.5

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the scope of rights claimed by the present invention. All other equivalent changes or modifications that do not depart from the spirit disclosed in the present invention shall be included in the present invention. within the scope of the patent application.

1a to 1c are SEM images of a preferred embodiment of the present invention. 2a to 2c are SEM images of another preferred embodiment of the present invention.

Claims (2)

A thermoplastic material formulation suitable for supercritical fluid injection foaming, comprising: thermoplastic material 96.5-99.3wt%, the thermoplastic elastomer comprises polyester thermoplastic elastomer; reactive modifier 0.2-2.0wt%, The reactive modifier includes epoxide and isocyanate silane; the inorganic nucleating agent is 0.5-1.5 wt %, and the inorganic nucleating agent includes white smoke and white smoke modified by aminosilane, and the ratio of the two is Between 97.5:2.5 to 95:5, the inorganic nucleating agent has a pore size of 27.9nm-30.5nm and a pore volume of 0.83-0.87cm ³ /g; wherein: the thermoplastic material formulation is foamed by supercritical fluid injection The foam has a Shore hardness of 88A and a tensile strength of 154.2kgf/cm ² . A thermoplastic formulation suitable for injection foaming of supercritical fluid as claimed in claim 1, wherein: the epoxide comprises polyfunctional glycidyl ester polymer, triglycidyl isocyanurate, and epoxy silane.

Images