Multilayer polymer structures and methods of making same

Abstract

A multilayer polymer structure includes a support layer and a first surface layer. The supporting layer comprises polyethylene terephthalate. The support layer has a melting point of 235 DEG C to 252 DEG C. The first surface layer is located on the first surface of the supporting layer, and the first surface layer comprises non-crystallized polyethylene terephthalate.

Description

Technical Field

[0001] The present invention relates to a multilayer polymer structure and a method for making the same. Background Art

[0002] In response to the rise of environmental awareness, the recycling of plastic products has gradually received attention. At present, many electronic products on the market are packaged with cardboard and a transparent plastic shell attached to the cardboard, so that consumers can directly view the electronic products located inside through the transparent plastic shell. Generally speaking, the material of this transparent plastic shell is a co-extruded material of polyethylene terephthalate (PET) and polyethylene terephthalate-1,4-cyclohexanedimethanol (PETG), with PET as the middle support layer and PETG as the surface adhesive layer. Although PETG and PET are both polyester materials, the plastic classification mark (resin identification code) of PETG is No. 7, while the plastic classification mark (resin identification code) of PET is No. 1, which makes PETG and PET difficult to recycle together. Therefore, there is an urgent need for a method to improve the recyclability of packaging materials. Summary of the invention

[0003] At least one embodiment of the present invention provides a multilayer polymer structure, which includes a support layer and a first surface layer. The support layer includes polyethylene terephthalate. The support layer has a melting point of 235 degrees Celsius to 252 degrees Celsius. The first surface layer is located on a first surface of the support layer, and the first surface layer includes non-crystallized polyethylene terephthalate.

[0004] At least one embodiment of the present invention provides a method for manufacturing a multilayer polymer structure, comprising the following steps: providing a first polyester pellet, wherein the first polyester pellet comprises polyethylene terephthalate, and the first polyester pellet has a melting point of 235 degrees Celsius to 252 degrees Celsius; providing a second polyester pellet, wherein the second polyester pellet comprises non-crystallized polyethylene terephthalate; forming a support layer and a first surface layer located on a first surface of the support layer by co-extrusion, wherein the raw material of the support layer comprises the first polyester pellet, and the raw material of the first surface layer comprises the second polyester pellet. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Figure 1 is a schematic cross-sectional view of a multilayer polymer structure according to an embodiment of the present invention. DETAILED DESCRIPTION

[0006] Figure 1 is a cross-sectional schematic diagram of a multilayer polymer structure according to an embodiment of the present invention. Figure 1The multilayer polymer structure 10 includes a support layer 100 and a first surface layer 210 located on the first surface 102 of the support layer 100 . In this embodiment, the multilayer polymer structure 10 further includes a second surface layer 220 located on the second surface 104 of the support layer 100 .

[0007] The support layer 100 includes polyethylene terephthalate (PET). In some embodiments, the polyethylene terephthalate in the support layer 100 may include virgin polyester resin, recycled polyester, or a combination thereof. Virgin polyester is a generally existing newly produced polyester. Recycled polyester may include physically recycled polyester and / or chemically recycled polyester. In some embodiments, polyester pellets are manufactured using virgin polyester and / or recycled polyester as raw materials, and then the support layer 100 is formed using the polyester pellets as raw materials.

[0008] For example, the method for obtaining recycled polyester includes: collecting various types of waste polyester resin materials, classifying the waste polyester resin materials according to their types, colors, and uses, and compressing and packaging the waste polyester resin materials and then transporting them to a waste treatment plant.

[0009] In some embodiments, the waste polyester resin material is recycled PET bottles, film materials, fibers, etc., but the present invention is not limited thereto. Other components on the waste polyester resin material (such as the bottle cap, label and adhesive of the PET bottle) are removed. Then, the waste polyester resin material is cut and crushed, and the bottle mouth, liner and bottle body of different materials in the PET bottle are separated by flotation and other methods. In addition, the crushed waste polyester resin material is dried to obtain the processed recycled polyester material (i.e., recycled polyethylene terephthalate (r-PET)), so as to facilitate the subsequent manufacturing process.

[0010] The recycled polyester material is further processed to obtain recycled polyester pellets. The recycled polyester pellets can be physically recycled polyester pellets or chemically recycled polyester pellets.

[0011] In some embodiments, physically recycled polyester resins refer to polyester resins obtained by physical recycling, including physically recycled conventional polyester resins and physically recycled modified polyester resins. Physically recycled conventional polyester resins do not have any functional additives added during the recycling process, while physically recycled modified polyester resins are prepared by adding functional additives (e.g., lubricants, colorants, weathering modifiers, and matte agents) during the recycling process to produce physically recycled modified polyester resins with different functions.

[0012] In some embodiments, the manufacturing method of chemically recycled polyester pellets includes: cutting recycled polyester materials (e.g., PET bottle flakes), and putting the cut bottle flakes into a chemical depolymerization liquid to break the polyester molecules in the recycled polyester material, thereby achieving the effect of depolymerizing the recycled polyester material, and further obtaining a polyester composition with a shorter molecular chain and an ester monomer composed of a diacid unit and two diol units, such as bis(hydroxyethyl) terephthalate (BHET). Then, separating and purifying the oligomer mixture, and then repolymerizing the oligomer mixture to obtain chemically recycled polyester pellets. In some embodiments, in the process of chemical reprocessing, functional additives (e.g., lubricants, colorants, weathering modifiers, and matte agents, etc.) can also be added to the oligomer mixture, and then repolymerized to obtain chemically recycled modified polyester pellets with different functions.

[0013] The polyethylene terephthalate in the support layer 100 is crystalline and thus has a melting point of 235 to 252 degrees Celsius. In some embodiments, the polyethylene terephthalate in the support layer 100 has a crystallinity of 9% or more at room temperature (about 23° C.). In some embodiments, the cooling crystallization temperature (Tcc) of the polyethylene terephthalate in the support layer 100 is 160 to 190° C.

[0014] The polyethylene terephthalate in the support layer 100 has an intrinsic viscosity (IV) of 0.72 dL / g to 0.84 dL / g, preferably between 0.76 dL / g and 0.80 dL / g. When the intrinsic viscosity is lower than 0.72, the material viscosity is too low, the extruded sheet has poor formability and poor impact strength. When the intrinsic viscosity is higher than 0.84, the material viscosity is too high, the production speed of the sheet is reduced by more than 20%, and the required processing temperature is high and energy-consuming. In some embodiments, the intrinsic viscosity of polyethylene terephthalate can be increased by a viscosity-increasing process, and the viscosity-increasing process includes solid viscosity-increasing and / or liquid viscosity-increasing.

[0015] The first surface layer 210 and the second surface layer 220 are respectively located on the first surface 102 and the second surface 104 of the support layer 110. The first surface layer 210 and the second surface layer 220 include amorphous PET. In some embodiments, the first surface layer 210 and the second surface layer 220 are formed by using polyester pellets of amorphous PET as raw materials.

[0016] In some embodiments, terephthalic acid (PTA) and ethylene glycol (EG) are subjected to an ester exchange reaction to form diethylene terephthalate (BHET). Afterwards, diethylene terephthalate (BHET) is copolymerized with a monomer having steric hindrance to form a non-crystallized polyethylene terephthalate. In some embodiments, the non-crystallized polyethylene terephthalate includes 18 mol% to 35 mol% of a monomer having steric hindrance. In some embodiments, the monomer having steric hindrance is selected from at least one of the following combinations: isophthalic acid, neopentyl glycol, phthalic acid, pentaerythritol, propylene glycol, isosorbide, and polyethylene glycol. By adjusting the content of the monomer having steric hindrance, the crystallization rate of polyethylene terephthalate can be slowed down to facilitate the preparation of non-crystallized polyethylene terephthalate. In some embodiments, the non-crystallized polyethylene terephthalate in the first surface layer 210 and the second surface layer 220 is a non-crystalline (no melting point) material. When the temperature is greater than its glass transition temperature, the material softens, so that it can be used as an adhesive layer. In some embodiments, the glass transition temperature of the non-crystallized polyethylene terephthalate in the first surface layer 210 and the second surface layer 220 is 60° C. to 80° C., and has no melting point and cooling crystallization temperature (Tcc).

[0017] The amorphous polyethylene terephthalate material is cut and granulated to obtain polyester pellets of amorphous polyethylene terephthalate. In some embodiments, the amorphous polyethylene terephthalate material is granulated by a screw extruder to form polyester pellets in granular form.

[0018] Finally, the polyester pellets of polyethylene terephthalate and the polyester pellets of non-crystallized polyethylene terephthalate are used as raw materials for co-extrusion to form the support layer 100, the first surface layer 210 and the second surface layer 220. The raw material of the support layer 100 includes the polyester pellets of polyethylene terephthalate (also referred to as the first polyester pellets), and the raw materials of the first surface layer 210 and the second surface layer 220 include the polyester pellets of non-crystallized polyethylene terephthalate (also referred to as the second polyester pellets). The first polyester pellets and the second polyester pellets are respectively put into an extruder to obtain a multi-layer polymer structure 10 by a co-extrusion process.

[0019] In some embodiments, the thickness T of the multilayer polymer structure 10 is 0.15 mm to 1.4 mm. In some embodiments, the thickness T1 of the support layer 100 accounts for 70% to 88% of the thickness T of the multilayer polymer structure 10, and the thickness T2 of the first surface layer 210 and the thickness T3 of the second surface layer 220 each account for 6% to 15% of the thickness T of the multilayer polymer structure 10.

[0020] In some embodiments, after the co-extrusion process is performed, the obtained multilayer polymer structure 10 is cooled, for example, by a cooling wheel. The cooled multilayer polymer structure 10 is then rolled up, and finally molded and heat-sealed (for example, high-frequency heat sealing, heat pressing, etc.) as required. In this embodiment, the softening temperature (or glass transition temperature) of the first surface layer 210 and the second surface layer 220 in the multilayer polymer structure 10 is lower than the softening temperature (or glass transition temperature) of the support layer 100, so the first surface layer 210 and the second surface layer 220 are easily softened after being heated, and can be used as an adhesive layer for bonding other components.

[0021] Table 1 provides a comparison of the composition and physical properties of non-crystallized polyethylene terephthalate containing different monomers having steric hindrance according to some embodiments and the physical properties of PETG.

[0022] Table 1

[0023]

[0024] In Table 1, no additional viscosity increasing process is performed on the non-crystallized polyethylene terephthalate of Examples 1 to 3, and the intrinsic viscosity of the non-crystallized polyethylene terephthalate is less than the intrinsic viscosity of the polyethylene terephthalate suitable for use in the support layer (0.72 dL / g to 0.84 dL / g). Table 2 provides a comparison of the properties of the multilayer polymer structures of some embodiments and some comparative examples. The multilayer polymer structures of Table 2 all include two surface layers and a support layer sandwiched between the surface layers.

[0025] Table 2

[0026]

[0027] As can be known from Table 2, with non-crystallized polyethylene terephthalate (APET) as the surface layer, the characteristic after heat sealing process (such as high frequency heat sealing, hot pressing, etc.) is similar to the characteristic of PETG. And the multilayer polymer structure in embodiment 4 and embodiment 5 has higher impact resistance than the multilayer polymer structure of comparative example 1 with PETG as the surface layer. In addition, the multilayer polymer structure of embodiment 4 to embodiment 6 does not break after the falling ball impact test, so that the multilayer polymer structure of embodiment 4 to embodiment 6 is suitable for packaging materials, cards, etc. of products (such as electronic products). In addition, since the plastic classification marks of non-crystallized polyethylene terephthalate and PET are all No. 1, the multilayer polymer structure obtained by using non-crystallized polyethylene terephthalate as the surface layer and using PET as the supporting layer can be easily recycled, so there is the advantage of energy saving, carbon reduction and environmental protection.

Claims

1. A multilayer polymer structure comprising: A support layer comprising polyethylene terephthalate, wherein the support layer has a melting point of 235 degrees Celsius to 252 degrees Celsius; as well as The first surface layer is located on the first surface of the support layer, and the first surface layer includes non-crystallized polyethylene terephthalate. 2 . The multilayer polymer structure according to claim 1 , wherein the first surface layer comprises 18 mol % to 35 mol % of a monomer having steric hindrance.

3. The multilayer polymer structure according to claim 2, wherein the monomer having steric hindrance is selected from at least one of the following groups: isophthalic acid, neopentyl glycol, phthalic acid, pentaerythritol, propylene glycol, isosorbide and polyethylene glycol.

4. The multilayer polymer structure of claim 1, further comprising: The second surface layer is located on a second surface of the support layer opposite to the first surface, and the second surface layer includes non-crystallized polyethylene terephthalate.

5. The multilayer polymer structure according to claim 4, wherein the thickness of the support layer accounts for 70% to 88% of the thickness of the multilayer polymer structure, and the thickness of the first surface layer and the thickness of the second surface layer each account for 6% to 15% of the thickness of the multilayer polymer structure.

6. A method for manufacturing a multilayer polymer structure, comprising: Providing a first polyester pellet, wherein the first polyester pellet comprises polyethylene terephthalate, and the first polyester pellet has a melting point of 235 degrees Celsius to 252 degrees Celsius; Providing a second polyester pellet, wherein the second polyester pellet comprises non-crystallized polyethylene terephthalate; A support layer and a first surface layer located on a first surface of the support layer are formed by co-extrusion, wherein the raw material of the support layer includes the first polyester pellets, and the raw material of the first surface layer includes the second polyester pellets.

7. The method for manufacturing a multilayer polymer structure according to claim 6, wherein the method of providing the second polyester pellet comprises: Transesterifying terephthalic acid and ethylene glycol to form diethylene terephthalate; The diethylene terephthalate is copolymerized with a monomer having steric hindrance to form the second polyester pellet containing non-crystallized polyethylene terephthalate. 8 . The method for manufacturing a multilayer polymer structure according to claim 7 , wherein the non-crystallized polyethylene terephthalate includes 18 mol % to 35 mol % of the monomer having steric hindrance.

9. The method for manufacturing a multilayer polymer structure according to claim 8, wherein the monomer having steric hindrance is selected from at least one of the following groups: isophthalic acid, neopentyl glycol, phthalic acid, pentaerythritol, propylene glycol, isosorbide and polyethylene glycol.

10. The method for manufacturing a multilayer polymer structure according to claim 6, further comprising: The support layer, the first surface layer located on the first surface of the support layer, and the second surface layer located on the second surface of the support layer opposite to the first surface are formed by co-extrusion, wherein the raw material of the second surface layer includes the second polyester particles.

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