PET (Polyethylene Terephthalate) bottom film and preparation method of PET bottom film plate

Abstract

The invention discloses a PET base film and a PET base film plate preparation method, and relates to the technical field of plates, the PET base film comprises PET resin, oleamide, silicon dioxide, an antioxidant and a flake mica sheet, the antioxidant is formed by mixing a hindered phenol antioxidant and a phosphite ester antioxidant, and the aspect ratio of the flake mica sheet is 80-150; the PET film is adopted to replace a traditional LVT plate bottom film, the characteristic that the intermolecular structure of the PET material is tighter is fully utilized, the barrier property of the material is remarkably improved, and therefore migration and precipitation of a plasticizer are effectively inhibited.

Description

Technical Field

[0001] This invention relates to the field of sheet technology, and specifically to a PET base film. Background Technology

[0002] LVT flooring is an environmentally friendly, reliable, and easy-to-install flooring that can highly reproduce the texture and feel of natural materials such as solid wood and marble. It offers a wide variety of colors and patterns to easily match different decorating styles. It comes with self-adhesive backing and release paper, which can be peeled off and installed, eliminating the need for traditional glue application and drying steps. This avoids glue overflow and pollution during on-site application, making the construction process cleaner.

[0003] To reduce plasticizer leaching, traditional LVT (Low Temperature Variation) adhesive flooring incorporates a 0.1mm PVC film as the base material. This film typically contains plasticizers. Under the influence of the adhesive, free plasticizers in the film leach out. This leaching creates channels between the PVC film sections. Over time, the plasticizers slowly leach from the LVT base material, penetrating the adhesive layer and diluting or damaging its structure. This significantly reduces the initial tack and holding power of the adhesive, potentially leading to problems such as product detachment after installation. Summary of the Invention

[0004] Purpose of the invention: The technical problem to be solved by the present invention is to provide a PET base film and a method for preparing PET base film sheets, which solves the problem of easy precipitation of plasticizer in LVT sheets.

[0005] Technical solution

[0006] To solve the above problems, the technical solution provided by the present invention is as follows:

[0007] A PET base film includes PET resin, oleamide, silica, antioxidant, and flake mica sheets, wherein the antioxidant is a mixture of hindered phenolic antioxidants and phosphite antioxidants, and the aspect ratio of the flake mica sheets is between 80 and 150.

[0008] Furthermore, the detailed proportions of each component in the PET base film are as follows (by mass): 100 parts PET resin, 0.05±0.01 parts oleamide, 0.01±0.005 parts hindered phenolic antioxidants and phosphite antioxidants, and 5-15 parts flaky mica sheets.

[0009] Furthermore, the ratio of the hindered phenolic antioxidant to the phosphite antioxidant is 2:1.

[0010] A method for preparing a PET base film sheet, comprising the preparation of the PET base film and the surface treatment of the PET base film.

[0011] Furthermore, the preparation of the PET base film includes pretreatment of raw materials, high-speed mixing, melt injection molding, biaxial stretching, and heat setting.

[0012] Furthermore, the PET resin needs to be vacuum dried, and the sheet-like mica sheets need to be mixed at high speed to ensure that the proportion of agglomerated sheets is less than 5%.

[0013] Furthermore, the bidirectional stretching includes longitudinal stretching and transverse stretching, wherein the longitudinal stretching has a stretching ratio of 4-5 times and the transverse stretching has a stretching ratio of 3-4 times.

[0014] Furthermore, the surface treatment of the PET base film requires coating the PET base film with adhesive, which is a thermoplastic polyurethane.

[0015] Furthermore, the adhesive formulation comprises, by weight parts, 100 parts polyester TPU resin, 15-25 parts hydrogenated rosin glycerol ester, and 0.1-0.3 parts hindered phenolic antioxidant.

[0016] Furthermore, the PET substrate is corona treated before the adhesive is applied.

[0017] Beneficial effects

[0018] Compared with the prior art, the technical solution provided by this invention has the following advantages:

[0019] This invention utilizes a PET film instead of the traditional LVT sheet base film, fully leveraging the denser intermolecular structure of PET material to significantly improve its barrier properties, thereby effectively inhibiting the migration and precipitation of plasticizers. Furthermore, flaky mica sheets with a high aspect ratio greater than 80 are added to the PET film. These mica sheets not only promote the crystallinity of PET, enhancing its mechanical properties and thermal stability, but their unique layered distribution structure also forms multiple barrier interfaces within the material, greatly extending the diffusion path of plasticizers. This multi-layered barrier mechanism works synergistically to further reduce the precipitation rate and total amount of plasticizers, significantly improving the product's environmental performance and service life. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the present invention; Detailed Implementation

[0021] To make the technical solution of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] Example 1

[0023] Combined with appendix Figure 1A PET base film, the formulation of which includes PET resin, oleamide, silica, antioxidant, and flake mica sheets, wherein the antioxidant is a mixture of hindered phenolic antioxidant and phosphite antioxidant in a ratio of 2:1.

[0024] PET resin is the main material for making PET film.

[0025] Oleamide is an internal lubricant used to reduce the viscosity of PET melt and improve extrusion flowability; at the same time, it forms a micro-lubricating layer on the film surface, reducing film roll adhesion. Oleamide can reduce the coefficient of friction of PET film from 0.4 to 0.2.

[0026] Hindered phenolic antioxidants are used to capture free radicals, while phosphite antioxidants decompose hydrogen peroxides; the two antioxidants work synergistically to inhibit thermal oxidative degradation during high-temperature extrusion, reducing the melt viscosity reduction rate during high-temperature extrusion from 15% to 5%.

[0027] Flake-shaped mica sheets can improve the crystallinity of PET. When added to PET resin, the mica sheets are distributed in layers, forming a multi-layer barrier interface, which further reduces the precipitation of plasticizers. The precipitation of plasticizers is inhibited through "crystallization-promoting coordination and physical barrier".

[0028] In conclusion, the detailed proportions of each component in the PET base film are as follows (by mass): 100 parts PET resin, 0.05±0.01 parts oleamide, 0.01±0.005 parts hindered phenolic antioxidants and phosphite antioxidants, and 5-15 parts flaky mica sheets.

[0029] The aspect ratio of the flaky mica sheets should be between 80 and 150. By synergistically optimizing both the aspect ratio and mass ratio of the flaky mica sheets, the performance of the flaky mica sheets in inhibiting plasticizer exudation in PET base films can be greatly improved.

[0030] Aspect ratio enhances physical barrier performance. Aspect ratio is the length-to-diameter ratio, which is the ratio between the length and thickness of a sheet-like mica sheet, i.e., L / D, where L is the sheet length and D is the thickness.

[0031] The aspect ratio of mica sheets directly determines their orientation and barrier efficiency in the PET matrix:

[0032] When the aspect ratio is less than 50, the mica flakes are short and tend to agglomerate in PET, failing to form a continuous barrier network. The migration path is only extended by 2-3 times, and the plasticizer exudation inhibition rate is less than 30%.

[0033] When the aspect ratio is greater than 80, the mica sheets are long and thin, making them easier to orient along the shear direction in the PET melt flow (more than 85% of the sheets can be oriented longitudinally through biaxial stretching process), forming a "layered" barrier structure. The migration path is extended to more than 80 times the original path, and the inhibition rate is greater than 80%.

[0034] Extreme case: When the aspect ratio is greater than 200, the mica sheets are prone to uneven dispersion, which can lead to local stress concentration and reduce the mechanical properties of the PET film (the elongation at break decreases by 15%). Therefore, the optimal aspect ratio is controlled between 80 and 150.

[0035] The significance of mass ratio: balancing barrier efficiency and overall performance

[0036] The amount of mica added needs to strike a balance between "barrier effect" and "PET matrix properties":

[0037] Mass ratio <5%: Insufficient mica flakes cannot form an effective barrier network, resulting in limited crystallization promotion. The plasticizer precipitation inhibition rate is only 40%-50%, and the improvement on the tensile strength of PET (from 50MPa to 52MPa) and heat shrinkage rate (from 0.5% to 0.4%) is not significant.

[0038] Mass ratio 5%-15%: As the amount added increases, the barrier network is gradually improved, the crystallinity continues to increase (the crystallinity reaches 58% at 10%), and the plasticizer precipitation inhibition rate increases from 60% (5%) to 90% (15%).

[0039] Mass ratio > 15%: Excessive dispersion of mica flakes leads to agglomeration, increases interface defects, reduces the mechanical properties of PET film (such as folding endurance), and increases processing difficulty (melt viscosity increases by 30%), resulting in an overall cost increase of more than 20%.

[0040] Therefore, a mass ratio of 5%-15% achieves a good balance, with the optimal mass ratio recommended at 10%-12%, balancing barrier efficiency and processing performance.

[0041] A method for preparing a PET base film sheet includes two parts: preparation of the PET base film and surface treatment of the PET base film.

[0042] The preparation of PET bottom film includes raw material pretreatment, high-speed mixing, melt injection molding, biaxial stretching, and heat setting.

[0043] 1. Raw material pretreatment:

[0044] PET resin raw materials are vacuum dried at 150-180℃ for 4-6 hours.

[0045] PET is highly hygroscopic, with an equilibrium water absorption rate of approximately 0.4%. Undried chips are prone to hydrolysis during high-temperature extrusion. The chemical formula for the reaction is... This leads to molecular chain breakage, a decrease in molecular weight, and a reduction in intrinsic viscosity, ultimately affecting the tensile strength and barrier properties of the film. High-temperature drying significantly reduces the moisture content within the PET film, thereby minimizing hydrolysis.

[0046] 2. High-speed mixing:

[0047] Add each component to a high-speed mixer in the specified proportions and mix thoroughly. Ensure the components are evenly dispersed.

[0048] Preferably, a high-speed mixer with a speed of 800-1200 rpm is used, the mixing time is 10-15 minutes, and the temperature is controlled at 40-50℃.

[0049] Flake mica sheets need to be dispersed by a high-speed mixer. Because mica sheets with high aspect ratio are prone to agglomeration due to van der Waals forces, high-speed shear force can break up the agglomerates and make them uniformly dispersed in the PET melt in the form of single flakes. The shear force of the flakes after high-speed mixing is observed by scanning electron microscopy. Only when the agglomerated flakes account for less than 5% can the flake mica sheets achieve the distribution state in PET resin.

[0050] 3. Melt casting:

[0051] The uniformly mixed material is placed in a heating device for heating. When the temperature reaches the material's melting point, the material gradually transforms into a uniform molten state. At this point, it is quickly injected into a pre-set mold, and the molding process is completed through casting. The heating temperature is 265-275 degrees Celsius.

[0052] 4. Biaxial stretching process:

[0053] Biaxial stretching can regulate crystallization and orientation, and improve overall performance. Biaxial stretching includes longitudinal stretching and transverse stretching.

[0054] Process parameters:

[0055] Longitudinal stretching (MD): Temperature 90-110℃ (above the glass transition temperature of PET and below the melting point), stretching ratio 4-5 times, speed 15-20m / min.

[0056] Transverse stretching (TD): Temperature 100-120℃, stretching ratio 3-4 times, speed 5-8m / min.

[0057] 5. Heat setting: Temperature 180-200℃, time 10-15 seconds, to produce PET base film.

[0058] PET base film surface treatment: Since PET base film cannot be directly adhered to the substrate, it needs to be treated on the PET surface by applying adhesive to bond the PET base film to the substrate. Thermoplastic polyurethane is applied to the PET surface as the adhesive.

[0059] 1. Adhesive formula:

[0060] The formulation, by weight, consists of 100 parts polyester TPU resin, 15-25 parts hydrogenated rosin glycerol ester, and 0.1-0.3 parts hindered phenolic antioxidant.

[0061] Polyester-type TPU resin is used as the main adhesive matrix, preferably polyester-type TPU with a molecular weight of 80,000-120,000 (melt index MI=50-100g / 10min, 180℃ / 2.16kg) and a hardness of 80-90A.

[0062] Hydrogenated rosin glycerol ester, a tackifying resin, with a softening point of 85-100℃ and a solubility parameter δ=8.5-9.0 (TPU δ=8.8-9.2), exhibits excellent compatibility.

[0063] Hindered phenolic antioxidants are used to inhibit the oxidative degradation of TPU during hot pressing (150-170℃), prevent the adhesive layer from yellowing and the molecular weight from decreasing, extend the shelf life of the adhesive, and enable the adhesive to remain free of obvious clumping for 6 months.

[0064] 2. Apply glue:

[0065] PET substrate pretreatment: Corona treatment of PET substrate,

[0066] PET has a low native surface tension of only about 40mN / m, and needs to be corona treated to reach ≥45mN / m (dyne pen test) to improve the wetting and adhesion of the adhesive.

[0067] Corona discharge parameters: power 3-5kW, speed 5-10m / min, no corona discharge breakdown marks (such as scorch marks) on the PET surface after treatment.

[0068] Coating temperature control:

[0069] The material tank temperature is 170±5℃ to maintain the melting of the adhesive, while the die head temperature is 175±5℃, slightly higher than the material tank temperature, to prevent the adhesive from forming a skin. Too low a temperature will cause the adhesive viscosity to increase and the coating to become uneven; too high a temperature will accelerate the oxidative degradation of TPU, easily causing the adhesive layer to yellow.

[0070] Coating speed and thickness:

[0071] Coating speed: 5-10 m / min, corresponding to a wet film thickness of 20-40 μm. Since TPU is solvent-free, its wet film is essentially a dry film. Speed ​​and thickness are adjusted in tandem: when increasing speed, reduce doctor blade pressure / gravure roller speed to prevent excessive thinness; when decreasing speed, increase pressure to prevent excessive thickness. Thickness deviation must be ≤±5% (monitored by an online thickness gauge).

[0072] LVT sheets using a PET base film consist of, from top to bottom, a UV layer, a wear-resistant layer, a colored film, an LVT substrate, and a PET base film.

[0073] UV Layer: UV coatings are mainly composed of oligomers, monomers, photoinitiators, and functional additives. The coating is applied to the surface of the wear-resistant layer using a roller coating method. When exposed to a light source such as an ultraviolet lamp or mercury lamp, the photoinitiator decomposes, generating active free radicals that initiate cross-linking of the oligomers. The main function of the UV coating is to improve the scratch resistance of the LVT and ensure the uniformity of its gloss. The basis weight of UV coatings is typically 10-17 g / m².

[0074] Wear-resistant layer: The wear-resistant layer is usually made of PVC, and its main function is to improve the wear resistance of LVT and prevent the pattern of the color film layer from being damaged.

[0075] Color film: Color film is usually made of PVC, and the texture pattern is printed on its surface through printing.

[0076] LVT substrate: The main components of LVT substrate are PVC resin, diisooctyl terephthalate (DOTP), calcium and zinc stabilizer, color powder and stone powder.

[0077] PET bottom film: The main function of PET bottom film is to reduce the release of plasticizers, and its thickness is 0.02mm.

[0078] LVT product manufacturing

[0079] LVT base material preparation:

[0080] The mixture is calendered into sheets according to requirements, wherein the ratio of PVC:DOTP:stone powder is 3:1.2:13.

[0081] Hot pressing process:

[0082] The wear-resistant layer, colored film, base material, and backing PET film are laid on the base pattern board in sequence, and the top layer is covered with an embossed board. The semi-finished product is then pressed through hot and cold pressing processes.

[0083] Tempering of coating

[0084] Coating: UV paint is applied to the product surface through a roller coating process and cured by UV curing lamp to form a thin, transparent protective layer.

[0085] Tempering: This process involves heating the product to release internal stress, reduce shrinkage, and improve product stability.

[0086] Except for the PET base film, the rest of the LVT sheet can be directly prepared using relatively mature technologies available on the market.

[0087] Comparative experiment:

[0088] Different base films are pasted onto LVT sheets. The base film type can be PET base film, PETG base film, or PVC base film. The LVT sheets are aged to induce the precipitation of plasticizers. Shear force tests are then performed on the aged LVT sheets. Because the LVT substrate can withstand different shear forces depending on whether the plasticizer has been precipitated or not, the shear force test can reflect the degree of plasticizer precipitation in the LVT substrate.

[0089] The components of the PET base film, by mass fraction, are: 100 parts PET resin, 0.05 parts oleamide, 0.01 parts hindered phenolic antioxidants and phosphite antioxidants in total, with a ratio of 2:1 between hindered phenolic antioxidants and phosphite antioxidants, and 12 parts flaky mica sheets with an aspect ratio of 80.

[0090] The component ratio of the polyester adhesive, by mass fraction, is 100 parts resin, 20 parts hydrogenated rosin glycerol ester, and 0.2 parts hindered phenolic antioxidant.

[0091] The PET base film and polyester adhesive are processed according to the above method to produce LVT sheets.

[0092] You can directly choose LVT boards with PETG or PVC backing films available on the market.

[0093] LVT board aging treatment: Place the product with good adhesive backing in an 80℃ oven for aging.

[0094] Experimental method: Cut a 2-inch * 3-inch sample and roll it with a standard weight with a contact area of ​​2 square inches against the steel plate five times. When measuring the shear force, take the maximum value.

[0095] Comparison of shear force data:

[0096]

[0097] Based on the above experimental data, it can be clearly concluded that LVT sheets with PET base film can withstand greater shear force. Therefore, compared with LVT sheets using PETG and PVC base films, LVT sheets using PET base film have a significantly better effect on inhibiting plasticizer exudation.

[0098] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A PET base film, characterized in that, It includes PET resin, oleamide, silica, antioxidant, and flake mica sheets, wherein the antioxidant is a mixture of hindered phenolic antioxidants and phosphite antioxidants, and the aspect ratio of the flake mica sheets is between 80 and 150.

2. The PET base film according to claim 1, characterized in that, The detailed proportions of each component in the PET base film are as follows (by mass): 100 parts PET resin, 0.05±0.01 parts oleamide, 0.01±0.005 parts hindered phenolic antioxidants and phosphite antioxidants, and 5-15 parts flaky mica sheets.

3. The PET base film according to claim 1, characterized in that, The ratio of the hindered phenolic antioxidant to the phosphite antioxidant is 2:

1.

4. A method for preparing a PET base film sheet, comprising the PET base film according to any one of claims 1-3, characterized in that, Preparation of PET base film and surface treatment of PET base film.

5. The method for preparing a PET bottom film sheet according to claim 4, characterized in that, The preparation of the PET base film includes raw material pretreatment, high-speed mixing, melt injection molding, biaxial stretching, and heat setting.

6. The method for preparing a PET bottom film sheet according to claim 5, characterized in that, The PET resin needs to be vacuum dried, and the sheet mica sheets need to be mixed at high speed to make the agglomerated sheet ratio less than 5%.

7. The method for preparing a PET base film sheet according to claim 5, characterized in that, The bidirectional stretching includes longitudinal stretching and transverse stretching, with the longitudinal stretching having a stretching ratio of 4-5 times and the transverse stretching having a stretching ratio of 3-4 times.

8. The method for preparing a PET bottom film sheet according to claim 4, characterized in that, The surface treatment of the PET base film requires coating the PET base film with adhesive, which is a thermoplastic polyurethane.

9. The method for preparing a PET bottom film sheet according to claim 8, characterized in that, The adhesive formulation comprises, by weight, 100 parts polyester TPU resin, 15-25 parts hydrogenated rosin glycerol ester, and 0.1-0.3 parts hindered phenolic antioxidant.

10. A method for preparing a PET base film sheet according to claim 8, characterized in that, The PET substrate is corona treated before the adhesive is applied.

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