Degradable resin capable of blowing film at low temperature, preparation method and degradable film

Abstract

The invention discloses degradable resin capable of being subjected to film blowing at low temperature, a preparation method and a degradable film. The degradable resin comprises degradable polyester and a polyglycolic acid mixture, and the polyglycolic acid mixture comprises a polyglycolic acid graft copolymer and a polyglycolic acid homopolymer; wherein the polyglycolic acid grafted copolymer takes polyolefin as a main chain, and a polyglycolic acid side chain is grafted on the main chain; on the basis that the total weight of the degradable polyester and the polyglycolic acid mixture is 100 parts by weight, the degradable polyester accounts for 60-95 parts, and the polyglycolic acid mixture accounts for 5-40 parts. The melting range of the polyglycolic acid mixture is wider, and the polyglycolic acid mixture is easier to melt at low temperature, so that the problem that the PGA is difficult to melt and crystallize during film blowing at low temperature can be effectively solved, and the comprehensive mechanical property of the final mulching film is effectively improved.

Description

Technical Field

[0001] The present invention belongs to the field of degradable materials, and particularly relates to a degradable resin that can be blown into a film at low temperature, and a low-temperature blown film ultra-thin high-performance degradable ground film. Background Art

[0002] Ground films are widely used in farmlands in China, playing roles such as water retention, moisture preservation, weed removal, and promoting crop yield increase. However, in recent years, traditional ground films mainly made of polyethylene and polyvinyl chloride are extremely difficult to degrade, with a degradation period reaching up to hundreds of years. Moreover, after the ground films age and break, they are difficult to recycle. Accumulating in the soil will cause land pollution, serious damage to the soil structure, loss of fertility, and reduction in crop yields. The long-term use of such ground films poses a long-term and difficult-to-solve hazard to the land. Therefore, biodegradable ground films with the same warming and moisturizing effects and that can be completely degraded without polluting the soil have received extensive attention.

[0003] Currently, in the market of degradable ground films, commonly used biodegradable polymer materials mainly include polylactic acid (PLA), polycaprolactone (PCL), polyhydroxyalkanoates (PHA), copolymers of butylene adipate and butylene terephthalate (PBAT), etc. Among them, PBAT is usually used as the main raw material for degradable ground films and is blended with other enhanced complementary materials to improve its comprehensive performance. However, such degradable ground films have certain defects in actual use: 1 The PBAT ground film has poor rigidity and low mechanical strength, and is prone to cracking during mechanical film laying and use; 2 The PBAT ground film has poor water barrier performance and is not suitable for crop planting in arid areas. And polyglycolic acid PGA is a kind of degradable material with high mechanical strength and excellent water barrier performance. Blending PGA as a reinforcing material with PBAT by melting can solve the above-mentioned disadvantages of PBAT ground films.

[0004] In Chinese Patent CN109575536A, modified mesoporous SiO 2 is used as a lightening filler to prepare a PGA / PBAT degradable ground film with a PGA mass content of 15%-45%. The thickness of the ground film is 10 μm.

[0005] In Chinese Patent CN114702800A, a high-barrier PGA / PBAT degradable ground film is prepared, with a PGA content of more than 60%. The PGA / PBAT blend particles are blown into a film at 220°C, and the thickness of the ground film is 20-30 μm, with excellent water barrier performance.

[0006] In the existing PGA / PBAT film technology, due to the relatively high melting point of PGA (220°C - 230°C) and the narrow crystallization / melting peak, the blowing temperature during film processing is relatively high, usually above 220°C. When blowing the film at a relatively high temperature (230°C): PBAT and PGA are prone to thermal degradation, resulting in a sticky film surface, poor opening property, and even inability to continuously blow the film due to too low melt strength; when blowing the film at a relatively low blowing temperature (not exceeding 220°C): at this time, a large amount of PGA still exists in the form of microcrystals and cannot be melted, resulting in too high blowing pressure and difficulty in continuously blowing the film. Moreover, low-temperature blowing causes the PGA crystals to be unable to recrystallize and orient during the film cooling process, resulting in poor mechanical properties and inability to play the role of enhancing the PBAT film with PGA. Summary of the Invention

[0007] In order to overcome the problems existing in the prior art and overcome the disadvantages of poor opening property of the PGA / PBAT film (especially the film for agricultural mulch) when blowing the film at high temperature and low mechanical strength when blowing the film at a relatively low temperature, the present invention provides a degradable resin that can be blown at low temperature and a low-temperature blown ultra-thin high-performance degradable film for agricultural mulch. When the degradable resin is applied to film blowing, it can effectively broaden the blowing temperature range of the PGA film, especially the PGA film for agricultural mulch, so that the PGA film for agricultural mulch still has good mechanical properties within a relatively low blowing temperature range (190°C - 220°C), and comprehensively improves its comprehensive mechanical properties.

[0008] The first aspect of the present invention is to provide a degradable resin that can be blown at low temperature, which comprises a mixture of a degradable polyester and polyglycolic acid. The polyglycolic acid mixture comprises a polyglycolic acid graft copolymer and a polyglycolic acid homopolymer; wherein, the polyglycolic acid graft copolymer has a polyolefin as the main chain, and polyglycolic acid side chains are grafted on the main chain.

[0009] The degradable polyester is selected from homopolymers and / or copolymers of degradable polyesters, preferably at least one of homopolymers selected from poly(butylene adipate-co-terephthalate), poly(butylene succinate-co-butylene terephthalate), polylactic acid, polycaprolactone, poly(propylene carbonate), poly(butylene succinate), and polyhydroxyalkanoates.

[0010] The polyglycolic acid graft copolymer is selected from graft copolymers with polyglycolic acid as the side chain; preferably, the polyglycolic acid graft copolymer comprises a polymer main chain and a polymer side chain grafted on the polymer main chain. The polymer main chain is a straight-chain carbon chain or a branched carbon chain, and the polymer side chain is a polyglycolic acid side chain; more preferably, based on 100 wt% of the polyglycolic acid mixture, the content of the polyglycolic acid graft copolymer is 0.1 wt% - 80 wt%, and the content of the polyglycolic acid homopolymer is 20 wt% - 99.9 wt%.

[0011] The weight-average molecular weight of the polyglycolic acid mixture is 150,000 to 1,200,000 g / mol, preferably 200,000 to 400,000 g / mol; and / or, the weight-average molecular weight of the polyglycolic acid graft copolymer in the polyglycolic acid mixture is 500,000 to 10,000,000 g / mol, preferably 1,000,000 to 6,000,000 g / mol; and / or, the weight-average molecular weight of the polyglycolic acid homopolymer in the polyglycolic acid mixture is 50,000 to 350,000 g / mol, preferably 100,000 to 200,000 g / mol.

[0012] Based on the total weight of the biodegradable polyester and the polyglycolic acid mixture being 100 parts by weight, the biodegradable polyester is 60 to 95 parts, and the polyglycolic acid mixture is 5 to 40 parts; preferably, based on the total weight of the biodegradable polyester and the polyglycolic acid mixture being 100 parts by weight, the biodegradable polyester is 65 to 95 parts, and the polyglycolic acid mixture is 5 to 35 parts.

[0013] The biodegradable resin further includes an auxiliary agent; preferably, based on the total weight of the biodegradable polyester and the polyglycolic acid mixture being 100 parts, the auxiliary agent is 0.08 to 76 parts, preferably 1 to 47 parts.

[0014] The auxiliary agent is selected from at least one of a nucleating agent, a chain extender, an antiblocking agent, and a stabilizer; preferably, based on the total weight of the biodegradable polyester and the polyglycolic acid mixture being 100 parts, the nucleating agent is 0.02 to 30 parts, the chain extender is 0.01 to 6 parts, the antiblocking agent is 0.02 to 10 parts, and the stabilizer is 0.03 to 30 parts.

[0015] The second aspect of the present invention is to provide a method for preparing a biodegradable resin that can be blown into a film at low temperature, preferably for preparing the biodegradable resin described in the first aspect of the present invention. The preparation method includes: mixing components including the biodegradable polyester, the polyglycolic acid mixture, and optionally an auxiliary agent, and melt-extruding and pelletizing to obtain the biodegradable resin.

[0016] The preparation method includes: (1) mixing the optional auxiliary agent to obtain an auxiliary agent mixture, (2) mixing the biodegradable polyester and the polyglycolic acid mixture and optionally adding the auxiliary agent mixture, and (3) melt-extruding, cooling, and pelletizing to obtain the biodegradable resin; preferably, the temperature of the melt-extrusion is 50 to 350 °C, preferably 50 to 300 °C.

[0017] The polyglycolic acid mixture is obtained as follows: materials including a polyolefin with a hydroxyl side group, a homopolymeric polyglycolic acid initiator, a polyglycolic acid monomer, and a catalyst are polymerized; preferably: the polyolefin with a hydroxyl side group is selected from at least one of ethylene-vinyl alcohol copolymer and polyvinyl alcohol homopolymer; and / or, the polyglycolic acid monomer is selected from at least one of glycolide and glycolic acid; and / or, the homopolymeric polyglycolic acid initiator is selected from at least one of a monohydric alcohol, a polyhydric alcohol, and an amine compound, preferably at least one of a monohydric alcohol, a polyhydric alcohol, and an amine compound with a boiling point higher than 160°C; and / or, the catalyst is selected from at least one of salt compounds corresponding to one or more elements among Group IIA, IIIA, IVA, VA, IVB, VIIB, VIII, and IIB metal elements, and organic guanidine compounds, preferably at least one of Sn salts, Bi salts, Mg salts, Al salts, Ca salts, Fe salts, Mn salts, Ti salts, and Zn salts.

[0018] More preferably, the weight ratio of the polyglycolic acid monomer to the polyolefin with a hydroxyl side group is 100:(0.001 - 10), preferably 100:(0.01 - 1); and / or, the weight ratio of the polyglycolic acid monomer to the homopolymeric polyglycolic acid initiator is 100:(0.001 - 10), preferably 100:(0.01 - 1); and / or, the weight ratio of the polyglycolic acid monomer to the catalyst is 100:(0.005 - 1), preferably 100:(0.01 - 0.2).

[0019] The third aspect of the present invention is to provide an ultrathin, high-strength, and easy-to-open degradable film, which is prepared from the degradable resin capable of blow molding at low temperature described in the first aspect of the present invention; preferably obtained by blow molding.

[0020] The fourth aspect of the present invention is to provide a preparation method of an ultrathin, high-strength, and easy-to-open degradable film, preferably for preparing the degradable film described in the third aspect of the present invention. The preparation method includes: melting and extruding, blow molding, and cooling the degradable resin described in the first aspect of the present invention to obtain the degradable film.

[0021] The fifth aspect of the present invention is to provide the application of the degradable film or the degradable film obtained by the preparation method in degradable ground films. Detailed Embodiments

[0022] One of the purposes of the present invention is to provide a degradable resin capable of blow molding at low temperature, which includes a degradable polyester and a polyglycolic acid mixture. The polyglycolic acid mixture includes a polyglycolic acid graft copolymer and a polyglycolic acid homopolymer; wherein, the polyglycolic acid graft copolymer has a polyolefin as the main chain, and polyglycolic acid side chains are grafted on the main chain.

[0023] Among them, the polyglycolic acid graft copolymer is a comb-shaped graft copolymer. The polyolefin main chain is a straight-chain carbon chain or a branched carbon chain, and preferably, it is derived from at least one of ethylene-vinyl alcohol copolymer and polyvinyl alcohol homopolymer.

[0024] In a preferred embodiment, the biodegradable polyester is selected from biodegradable polyester homopolymers and / or biodegradable polyester copolymers, preferably at least one of the homopolymers of polybutylene adipate / terephthalate, poly(butylene succinate / butylene terephthalate), polylactic acid, polycaprolactone, poly(propylene carbonate), polybutylene succinate, and polyhydroxyalkanoate.

[0025] In a preferred embodiment, based on the total weight of the biodegradable polyester and the polyglycolic acid mixture being 100 parts by weight, the biodegradable polyester is 60 to 95 parts, and the polyglycolic acid mixture is 5 to 40 parts.

[0026] For example, based on the total weight of the biodegradable polyester and the polyglycolic acid mixture being 100 parts by weight, the biodegradable polyester is 60 parts, 65 parts, 70 parts, 75 parts, 80 parts, 85 parts, 90 parts, or 95 parts, and the polyglycolic acid mixture is 5 parts, 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts, or 40 parts.

[0027] In a further preferred embodiment, based on the total weight of the biodegradable polyester and the polyglycolic acid mixture being 100 parts by weight, the biodegradable polyester is 65 to 95 parts, and the polyglycolic acid mixture is 5 to 35 parts.

[0028] In a still further preferred embodiment, based on the total weight of the biodegradable polyester and the polyglycolic acid mixture being 100 parts by weight, the biodegradable polyester is 70 to 95 parts, and the polyglycolic acid mixture is 5 to 30 parts, such as 5 to 25 parts.

[0029] In a preferred embodiment, the polyglycolic acid graft copolymer includes a polymer main chain and polymer side chains grafted onto the polymer main chain. The polymer main chain is a straight-chain carbon chain or a branched carbon chain (preferably a straight-chain carbon chain), and the polymer side chains are polyglycolic acid side chains.

[0030] Among them, the polymer main chain is a polyolefin chain. Optionally, unreacted hydroxyl side groups remain on the side groups of the polymer main chain.

[0031] Compared with traditional homopolymer PGA, such polyglycolic acid mixtures have the characteristics of a wider crystallization melting peak, a wider molecular weight distribution, and containing oligomers. On the one hand, the polyglycolic acid mixture has a wider melting peak compared to pure PGA, which can effectively solve the problem of poor mechanical properties of the obtained film during low-temperature blown film of PGA, and at the same time enable it to have good opening properties; on the other hand, the oligomers therein can act as compatibilizers to effectively improve the compatibility between the polyglycolic acid mixture and biodegradable polyesters (such as PBAT). Thus, by using the polyglycolic acid mixture of the present invention as a reinforcing material, the blown film temperature of the PGA mulch film can be effectively broadened, and the overall mechanical properties and opening properties of the PGA mulch film can be significantly improved.

[0032] In a preferred embodiment, the polyglycolic acid mixture is obtained as follows: materials including polyolefin with hydroxyl side groups, homopolymer polyglycolic acid initiator, polyglycolic acid monomer, and catalyst are polymerized.

[0033] Among them, the polyglycolic acid monomer refers to a monomer that can be polymerized to prepare polyglycolic acid.

[0034] In a further preferred embodiment, the polyolefin with hydroxyl side groups is selected from at least one of ethylene-vinyl alcohol copolymer and polyvinyl alcohol homopolymer; and / or, the polyglycolic acid monomer is selected from at least one of glycolide and glycolic acid; and / or, the homopolymer polyglycolic acid initiator is selected from at least one of monohydric alcohols, polyhydric alcohols, and amine compounds, preferably at least one of monohydric alcohols, polyhydric alcohols, and amine compounds with a boiling point higher than 160°C, more preferably at least one of butanediol, hexanediol, n-hexanol, ethylene glycol, glycerol, serine alcohol, leucinol, pentaerythritol, sorbitol, xylitol, amino acids, phenol, hydroquinone, resorcinol, cinnamyl alcohol, aniline, cinnamylamine, p-phenylenediamine, m-phenylenediamine, and dodecanediamine; and / or, the catalyst is selected from at least one of salt compounds and organic guanidine compounds corresponding to one element or multiple elements among Group IIA, IIIA, IVA, VA, IVB, VIIB, VIII, and IIB metal elements, preferably at least one of Sn salts, Bi salts, Mg salts, Al salts, Ca salts, Fe salts, Mn salts, Ti salts, and Zn salts, preferably Sn salts, such as stannous octanoate.

[0035] In a further preferred embodiment, the weight ratio of the polyglycolic acid monomer to the polyolefin with hydroxyl side groups is 100:(0.001 - 10), preferably 100:(0.01 - 1); and / or, the weight ratio of the polyglycolic acid monomer to the homopolymer polyglycolic acid initiator is 100:(0.001 - 10), preferably 100:(0.01 - 1); and / or, the weight ratio of the polyglycolic acid monomer to the catalyst is 100:(0.005 - 1), preferably 100:(0.01 - 0.2).

[0036] For example, the weight ratio of the glycolic acid monomer to the polyolefin with a hydroxyl side group is 100:0.001, 100:0.005, 100:0.01, 100:0.05, 100:0.1, 100:0.5, 100:1, 100:2, 100:3, 100:4, 100:5, 100:6, 100:7, 100:8, 100:9, or 100:10; and / or, the weight ratio of the glycolic acid monomer to the homopolymeric glycolic acid initiator is 100:0.001, 100:0.005, 100:0.01, 100:0.05, 100:0.1, 100:0.5, 100:1, 100:2, 100:3, 100:4, 100:5, 100:6, 100:7, 100:8, 100:9, or 100:10; and / or, the weight ratio of the glycolic acid monomer to the catalyst is 100:0.005, 100:0.01, 100:0.1, 100:0.2, 100:0.4, 100:0.6, 100:0.8, or 100:1.

[0037] In the present invention, the materials for preparing the glycolic acid mixture further contain an antioxidant, which can be selected from the antioxidants commonly used in the art; the dosage of the antioxidant is the dosage commonly used in the processing and preparation in the art. Preferably but not limited to, the weight ratio of the glycolic acid monomer to the antioxidant is 100:(0 - 2), preferably 100:(0.01 - 1), for example, 100:0.01, 100:0.05, 100:0.1, 100:0.2, 100:0.5, 100:0.8, 100:1, 100:1.2, 100:1.5, 100:1.8, or 100:2.

[0038] In a preferred embodiment, the obtaining (or polymerization) of the glycolic acid mixture is carried out at 140 - 280 °C, preferably 150 - 260 °C, more preferably 160 - 240 °C, for example, at one of the point values of 140 °C, 150 °C, 160 °C, 180 °C, 200 °C, 220 °C, 240 °C, 260 °C, or 280 °C, or in sequence of multiple point values, or within the range of any two point values.

[0039] In a further preferred embodiment, the obtaining (or polymerization) of the glycolic acid mixture is carried out in a screw extruder (such as a twin-screw extruder). Preferably, the screw speed is 5 - 300 rpm, preferably 40 - 150 rpm.

[0040] In a preferred embodiment, the weight-average molecular weight of the polyglycolic acid mixture (as a whole) is 150,000 to 1,200,000 g / mol, preferably 200,000 to 400,000 g / mol, such as 150,000, 200,000, 250,000, 300,000, 400,000, 600,000, 800,000, 1,000,000 or 1,200,000 g / mol.

[0041] In a further preferred embodiment, the molecular weight distribution index of the polyglycolic acid mixture (as a whole) is 1.5 to 20.0, preferably 2.0 to 3.5, such as 1.5, 2.0, 2.5, 3.0, 3.5, 5.0, 8.0, 10.0, 12.0, 15.0, 18.0 or 20.0.

[0042] Among them, the number of molecular weight distribution peaks of the polyglycolic acid mixture is at least 2, preferably 2 to 4, such as 2 or 3.

[0043] In a preferred embodiment, the weight-average molecular weight of the polyglycolic acid graft copolymer in the polyglycolic acid mixture (or corresponding to the high molecular weight peak in the GPC spectrum of the polyglycolic acid mixture) is 500,000 to 10,000,000 g / mol, preferably 1,000,000 to 6,000,000 g / mol, such as 500,000 g / mol, 1,000,000 g / mol, 2,000,000 g / mol, 4,000,000 g / mol, 6,000,000 g / mol, 8,000,000 g / mol or 10,000,000 g / mol.

[0044] In a further preferred embodiment, the polydispersity index of the polyglycolic acid graft copolymer in the polyglycolic acid mixture (or corresponding to the high molecular weight peak in the GPC spectrum of the polyglycolic acid mixture) can be 1.01 to 3.0, preferably 1.05 to 1.5, such as 1.01, 1.05, 1.1, 1.2, 1.3, 1.4, 1.5, 1.8, 2.0, 2.2, 2.5, 2.8 or 3.0.

[0045] In a preferred embodiment, the weight-average molecular weight of the polyglycolic acid homopolymer in the polyglycolic acid mixture (or corresponding to the low molecular weight peak in the GPC spectrum of the polyglycolic acid mixture) is 50,000 to 350,000 g / mol, preferably 100,000 to 200,000 g / mol, such as 50,000 g / mol, 100,000 g / mol, 150,000 g / mol, 200,000 g / mol, 250,000 g / mol, 300,000 g / mol or 350,000 g / mol.

[0046] In a further preferred embodiment, the polydispersity index of the polyglycolic acid homopolymer in the polyglycolic acid mixture (or corresponding to the low molecular weight peak in the GPC spectrum of the polyglycolic acid mixture) is 1.0 to 3.0, preferably 1.4 to 2.9, such as 1.0, 1.5, 2.0, 2.5 or 3.0.

[0047] In a preferred embodiment, based on 100 wt% of the polyglycolic acid mixture, the content of the polyglycolic acid graft copolymer is 0.1 wt% to 80 wt%, and the content of the polyglycolic acid homopolymer is 20 wt% to 99.9 wt%.

[0048] For example, based on 100 wt% of the polyglycolic acid mixture, the content of the polyglycolic acid graft copolymer is 0.1 wt%, 0.5 wt%, 1 wt%, 5 wt%, 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt% or 80 wt%, and the content of the polyglycolic acid homopolymer is 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, 80 wt%, 90 wt% or 99.9 wt%.

[0049] In a further preferred embodiment, based on 100 wt% of the polyglycolic acid mixture, the content of the polyglycolic acid graft copolymer is 1 wt% to 30 wt%, and the content of the polyglycolic acid homopolymer is 70 wt% to 99 wt%.

[0050] In a preferred embodiment, the melt flow rate (MFR) of the polyglycolic acid mixture under the conditions of 230 °C / 2.16 kg is below 20 g / 10 min, preferably 0.01 to 20 g / 10 min, more preferably 0.5 to 10 g / 10 min. For example, it can be 0.5 g / 10 min, 1 g / 10 min, 2 g / 10 min, 3 g / 10 min, 4 g / 10 min, 5 g / 10 min, 6 g / 10 min, 7 g / 10 min, 8 g / 10 min, 9 g / 10 min or 10 g / 10 min, and any interval composed of any two numerical values.

[0051] In a preferred embodiment, the degradable resin further includes an additive.

[0052] In a further preferred embodiment, the additive is selected from at least one of a nucleating agent, a chain extender, an antiblocking agent, and a stabilizer.

[0053] In a further preferred embodiment:

[0054] The nucleating agent is selected from the nucleating agents commonly used in the art, preferably but not limited to at least one of nanocrystalline cellulose, talcum powder, silica, and plate-shaped calcium carbonate. In addition to improving the crystallization performance of the material, the nucleating agent also has functions such as increasing the melt compatibility and improving the water resistance.

[0055] The chain extender is selected from chain extenders commonly used in the art, preferably but not limited to one or more selected from compounds and / or polymers that can react with carboxyl groups and / or hydroxyl groups, compounds and / or polymers containing multiple epoxy functional groups. Preferably, the chain extender is selected from at least one of polyfunctional isocyanate compounds, polyfunctional epoxy compounds, and graft polymers with epoxy groups in the side chain (such as ADR). More preferably, the chain extender is selected from at least one of hexamethylene diisocyanate, diphenylmethane diisocyanate, toluene diisocyanate, and a terpolymer of styrene-methyl methacrylate-glycidyl methacrylate (ADR); and / or,

[0056] The antiblocking agent is selected from antiblocking agents commonly used in the art, preferably but not limited to at least one selected from organic acids and their salts, preferably at least one of oleic acid amide, erucic acid amide, stearic acid amide, sodium stearate, and N,N'-ethylenebisstearamide; and / or,

[0057] The stabilizer is selected from stabilizers commonly used in the art, preferably but not limited to at least one selected from ultraviolet absorbers, light stabilizers, antioxidants, and hydrolysis-resistant agents; preferably: the ultraviolet absorber is selected from at least one of benzotriazole compounds, benzoxazine compounds, benzotriazole compounds, aniline compounds, triazine compounds, and benzophenone compounds, and is further preferably at least one of UV-P, UV-234, UV-326, UV-327, UV-328, UV-329, and UV-531; and / or, the light stabilizer is selected from at least one of hindered amine compounds and hindered phenol compounds, and is further preferably at least one of Chimassorb 944, Tinuvin 292, Tinuvin 622, Tinuvin 770, and Tinuvin 783; and / or, the antioxidant is selected from hindered phenol and phosphite antioxidants and any combination thereof, and is preferably at least one of 168, 264, 300, 425, 626, 627, 1010, and 1076; and / or, the hydrolysis-resistant agent is selected from carbodiimide compounds, such as hydrolysis-resistant agent Hymax 1010.

[0058] In a preferred embodiment, based on 100 parts by weight of the total weight of the biodegradable polyester and the polyglycolic acid mixture, the auxiliary agent is 0.08 to 76 parts, preferably 1 to 47 parts.

[0059] In a further preferred embodiment, based on 100 parts by weight of the total weight of the biodegradable polyester and the polyglycolic acid mixture, the nucleating agent is 0.02 to 30 parts, the chain extender is 0.01 to 6 parts, the antiblocking agent is 0.02 to 10 parts, and the stabilizer is 0.03 to 30 parts.

[0060] For example, based on 100 parts by weight of the total weight of the degradable resin and the polyglycolic acid mixture, the nucleating agent is 0.02 parts, 0.05 parts, 1 part, 5 parts, 10 parts, 15 parts, 20 parts, 25 parts or 30 parts, the chain extender is 0.01 part, 0.1 part, 0.5 part, 1 part, 2 parts, 3 parts, 4 parts, 5 parts or 6 parts, the antiblocking agent is 0.02 part, 0.05 part, 0.1 part, 0.5 part, 1 part, 2 parts, 4 parts, 6 parts, 8 parts or 10 parts, and the stabilizer is 0.03 part, 0.05 part, 0.1 part, 0.5 part, 1 part, 5 parts, 10 parts, 15 parts, 20 parts, 25 parts or 30 parts.

[0061] In a further preferred embodiment, based on 100 parts by weight of the total weight of the degradable polyester and the polyglycolic acid mixture, the nucleating agent is 1 to 20 parts, the chain extender is 0.05 to 2 parts, the antiblocking agent is 0.05 to 5 parts, and the stabilizer is 0.03 to 20 parts.

[0062] Preferably, the stabilizer can be composed of one or two or more components of ultraviolet absorbers, light stabilizers, antioxidants, and hydrolysis-resistant agents added in any proportion as required. Preferably, based on 100 parts by weight of the total weight of the degradable resin and the polyglycolic acid mixture, the added ultraviolet absorber, light stabilizer, antioxidant, and hydrolysis-resistant agent are each independently 0 to 5 parts and not all 0 at the same time.

[0063] The second object of the present invention is to provide a method for preparing a degradable resin that can be blown into a film at low temperature, preferably for preparing the degradable resin of the first object of the present invention. The preparation method includes: mixing components including the degradable polyester, the polyglycolic acid mixture and optional additives, and melt-extruding and pelletizing to obtain the degradable resin.

[0064] In a preferred embodiment, the preparation method includes: (1) mixing the optional additives to obtain an additive mixture, (2) mixing the degradable polyester and the polyglycolic acid mixture and optionally adding the additive mixture, and (3) melt-extruding, cooling, and pelletizing to obtain the degradable resin.

[0065] In a further preferred embodiment, the temperature of the melt extrusion is 50 to 350 °C, preferably 50 to 300 °C.

[0066] For example, the temperature of the melt extrusion is 50 °C, 100 °C, 150 °C, 200 °C, 250 °C, 300 °C or 350 °C.

[0067] According to an embodiment of the present invention, the melt extrusion may be a common melt extrusion method such as a twin-screw extruder, an internal mixer, a continuous melt mixer, a single-screw extruder or a multi-screw extruder, etc. Preferably, a twin-screw extruder is used, and a co-rotating or counter-rotating twin-screw extruder can be used. Among them, for conventional processes such as screw speed, the parameter indicators commonly used in the prior art can be adopted. Preferably but not limited to, the screw speed of the twin-screw extruder and / or the single-screw extruder is 5 to 500 rpm, preferably 50 to 300 rpm, more preferably 100 to 250 rpm. For example, the screw speed of the twin-screw extruder and / or the single-screw extruder is 5 rpm, 10 rpm, 50 rpm, 100 rpm, 150 rpm, 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm or 500 rpm. The twin-screw extruder of the present invention includes but is not limited to: the Micro 27 twin-screw extruder produced by Leistritz Company in Germany, which has the function of switching between co-rotating and counter-rotating; the co-rotating twin-screw extruders and internal mixers of models such as PolyLab HAAKE TM Rheomix OS, EuroLab, MiniLab, etc., and the ZSK 30 co-rotating parallel twin-screw extruder produced by Coperion Company in Germany.

[0068] In a preferred embodiment, the polyglycolic acid mixture is obtained as follows: materials including a polyolefin with a hydroxyl side group, a homopolymeric polyglycolic acid initiator, a polyglycolic acid monomer, and a catalyst are polymerized.

[0069] In a further preferred embodiment, the polyolefin with a hydroxyl side group is selected from at least one of ethylene-vinyl alcohol copolymer and polyvinyl alcohol homopolymer; and / or, the polyglycolic acid monomer is selected from at least one of glycolide and glycolic acid; and / or, the homopolymeric polyglycolic acid initiator is selected from at least one of a monohydric alcohol, a polyhydric alcohol, and an amine compound, preferably at least one of a monohydric alcohol, a polyhydric alcohol, and an amine compound with a boiling point higher than 160 °C, more preferably at least one of butanediol, hexanediol, n-hexanol, ethylene glycol, glycerol, serinol, leucinol, pentaerythritol, sorbitol, xylitol, amino acid, phenol, hydroquinone, resorcinol, cinnamyl alcohol, aniline, cinnamylamine, p-phenylenediamine, m-phenylenediamine, dodecane diamine; and / or, the catalyst is selected from at least one of salt compounds and organic guanidine compounds corresponding to one or more elements of Group IIA, IIIA, IVA, VA, IVB, VIIB, VIII, and IIB metal elements, preferably at least one of Sn salts, Bi salts, Mg salts, Al salts, Ca salts, Fe salts, Mn salts, Ti salts, and Zn salts, preferably Sn salts, such as stannous octanoate.

[0070] In a further preferred embodiment, the weight ratio of the glycolic acid monomer to the polyolefin with hydroxyl side groups is 100:(0.001 - 10), preferably 100:(0.01 - 1); and / or, the weight ratio of the glycolic acid monomer to the homopolymeric glycolic acid initiator is 100:(0.001 - 10), preferably 100:(0.01 - 1); and / or, the weight ratio of the glycolic acid monomer to the catalyst is 100:(0.005 - 1), preferably 100:(0.01 - 0.2).

[0071] In a preferred embodiment, the obtaining (or polymerization) of the glycolic acid mixture is carried out at 140 - 280°C, preferably 150 - 260°C, more preferably 160 - 240°C, for example, at a single point value of 140°C, 150°C, 160°C, 180°C, 200°C, 220°C, 240°C, 260°C or 280°C, or successively at multiple point values, or within the range of any two point values.

[0072] In a further preferred embodiment, the polymerization of the glycolic acid mixture is carried out in a screw extruder (such as a twin-screw extruder). Preferably, the screw speed is 5 - 300 rpm, preferably 40 - 150 rpm.

[0073] In the preparation method of the second object of the present invention, the amounts of the degradable polyester, the glycolic acid mixture, and the additive are the same as those of the degradable resin in the first object of the present invention, which are hereby incorporated by reference in their entirety.

[0074] The third object of the present invention is to provide an ultrathin, high-strength, and easy-to-open degradable film, which is prepared from the degradable resin capable of blow molding at low temperature described in the first object of the present invention. The breaking strength of the tear-resistant degradable film in the MD direction is 10 - 60 Mpa (preferably 14 - 40 Mpa), and the breaking strength in the CD direction is 5 - 30 MPa (preferably 6 - 25 MPa); the elongation at break of the tear-resistant degradable film in the MD direction is 100 - 600% (preferably 120 - 500%), and the elongation at break in the CD direction is 100 - 600% (preferably 150 - 500%).

[0075] In the present invention, the selection and amount of the degradable polyester, the glycolic acid mixture, and the optional additive in the degradable film are the same as those of the degradable resin in the first object of the present invention.

[0076] In a preferred embodiment, the thickness of the degradable film is 4 - 20 μm, preferably 5 - 10 μm, for example, 4 μm, 6 μm, 8 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm or 20 μm.

[0077] In a preferred embodiment, the degradable film is obtained by blown film extrusion of the degradable resin capable of blown film extrusion at low temperature as one of the objects of the present invention.

[0078] In the present invention, a polyglycolic acid mixture with a multi-molecular weight distribution, including a polyglycolic acid graft copolymer and a polyglycolic acid homopolymer, is used as a reinforcing material, which can effectively reduce the blown film temperature of the degradable film, greatly improve the opening property of the degradable film, and enhance the mechanical properties of the mulch film at the same time.

[0079] One of the objects of the present invention is to provide a method for preparing a degradable film that is ultra-thin, high-strength, and easy to open, preferably for preparing the degradable film described in the third object of the present invention. The preparation method includes: melting and extruding a degradable resin, blowing the film, and cooling to obtain the degradable film.

[0080] In a preferred embodiment, the temperature of the melt extrusion is 170 - 230 °C, preferably 180 - 220 °C, such as 170 °C, 180 °C, 190 °C, 200 °C, 210 °C, 220 °C, or 230 °C.

[0081] Among them, compared with the homopolymer PGA / degradable polyester film, the melt extrusion temperature of the degradable film of the present invention is wider.

[0082] In a preferred embodiment, the melt extrusion is carried out using a single-screw extruder. Preferably, the screw speed of the single-screw extruder is 5 - 200 rpm, preferably 10 - 150 rpm, such as 5 rpm, 10 rpm, 20 rpm, 40 rpm, 60 rpm, 80 rpm, 100 rpm, 120 rpm, 140 rpm, 160 rpm, 180 rpm, or 200 rpm.

[0083] One of the objects of the present invention is to provide the application of the degradable film described in the third object of the present invention or the degradable film obtained by using the preparation method described in the fourth object of the present invention in degradable mulch films.

[0084] The present invention uses the polyglycolic acid mixture as a biodegradable plastic film reinforcing material, and this polyglycolic acid mixture includes a grafted polyglycolic acid copolymer and a polyglycolic acid homopolymer. Such a grafted polyglycolic acid copolymer is formed by copolymerizing polyglycolic acid with a polyolefin having hydroxyl groups on its surface. Compared with traditional homopolymer PGA, such a polyglycolic acid mixture has a wider crystallization melting peak and a wider molecular weight distribution, and has the characteristic of containing oligomers. On the one hand, the polyglycolic acid mixture contained in the present invention has a wider melting peak compared to pure PGA, which can effectively solve the problem of poor mechanical properties of the film obtained during low-temperature blown film of PGA, and at the same time enable it to have good opening properties; on the other hand, the polyglycolic acid mixture contains oligomers of PGA-g-PE with hydroxyl groups in the side chain, which can be used as a compatibilizer to effectively improve the compatibility between PGA and PBAT. Thus, by using the polyglycolic acid mixture of the present invention as a reinforcing material, the blown film temperature of the PGA plastic film can be effectively broadened, and the overall mechanical properties and opening properties of the PGA plastic film can be significantly improved.

[0085] In the ranges and any values disclosed in the present invention, the endpoints and any values of the ranges are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein. In the following text, in principle, the various technical solutions can be combined with each other to obtain new technical solutions, which should also be regarded as specifically disclosed herein.

[0086] Compared with the prior art, the present invention has the following beneficial effects:

[0087] (1) The present invention can effectively broaden the blown film temperature of the PGA plastic film, and its lowest blown film temperature is far lower than the blown film temperature (220 °C - 230 °C) of the PGA plastic film on the market. At low blown film temperatures, there are some unmolten PGA crystals in the plastic film, which significantly increases the roughness of the film, can improve the anti-sticking property, and at this time, PBAT is not easily thermally degraded. It solves the problem of poor opening property of the PGA plastic film prepared in the existing products.

[0088] (2) The present invention uses the polyglycolic acid mixture as a plastic film reinforcing material. By utilizing the wider melting range of the polyglycolic acid mixture, which is more easily melted at low temperatures, it can effectively solve the problem that PGA is difficult to melt and crystallize during low-temperature blown film, thereby effectively improving the comprehensive mechanical properties of the final plastic film.

[0089] (3) In the present invention, the polyglycolic acid mixture is used as a plastic film reinforcing material, and it can also be used as a compatibilizer to effectively improve the compatibility and final properties of PGA and PBAT. Description of the Drawings

[0090] Figure 1 DSC curves of the degradable resins of Example 4 and Comparative Example 1; A: First heating, B: Cooling.

[0091] Figure 2 Second heating of the DSC curves of the P-degradable resins of Example 4 and Comparative Example 1

[0092] Figure 3 DSC curves of the degradable resins of Example 6 and Comparative Example 2; A: First heating, B: Cooling.

[0093] Figure 4 Mechanical properties in the MD direction of the mulch films blown from the degradable resins of Examples 4 to 6 and Comparative Examples 1 and 3 at 190 °C.

[0094] Figure 5 Mechanical properties in the CD direction of the mulch films blown from the degradable resins of Examples 4 to 6 and Comparative Examples 1 and 3 at 190 °C.

[0095] Figure 6 Elongation at break of the mulch films of the degradable resins of Example 4 and Comparative Example 1 at 220 °C.

[0096] The present invention will be specifically described below in conjunction with specific embodiments. It is necessary to point out here that the following embodiments are only for further illustration of the present invention and cannot be construed as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art to the present invention based on the content of the present invention still fall within the protection scope of the present invention.

[0097] In addition, it should be noted that, among the various specific technical features described in the following specific embodiments, they can be combined in any appropriate manner without conflict. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods.

[0098] In addition, any combination can be made between various different embodiments of the present invention as long as it does not violate the idea of the present invention. The technical solutions formed thereby belong to a part of the original disclosure content of this specification and also fall within the protection scope of the present invention.

[0099] The raw materials used in the examples and comparative examples, if not specifically limited, are all disclosed in the prior art, for example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0100] The test instruments and test conditions used in the examples are as follows:

[0101] Method for measuring melt index (MFR): The test was carried out on a CEAST MF20 melt flow rate tester manufactured by Instron Corporation in the United States. The test temperature was 230 °C, the load weight was 2.16 kg, and the preheating time was 4 min.

[0102] Thermal performance analysis (DSC): The test was carried out on a Discovery series differential scanning calorimeter (DSC) produced by TA Instruments. The processing software was TA Instruments Trios version 3.1.5. This DSC was equipped with a Refrigerated Cooling System 90 mechanical refrigeration accessory. The test atmosphere was nitrogen at 50 mL / min, and the required sample amount for the test was 5 - 10 mg. The test procedure was as follows: First, the temperature was stabilized at 40 °C, then it was heated to 220 °C at a rate of 10 °C / min and held for 1 min. After that, it was cooled to -50 °C at a rate of 10 °C / min and held for 1 min, and then heated to 220 °C at a rate of 10 °C / min. The cooling process and the second heating process were recorded to study the thermal performance of the sample. Through DSC testing, the crystallization temperature (T c ), melting temperature (T m ), glass transition (T g ), enthalpy change (H) and other information of the sample could be directly obtained by the software.

[0103] Film stretching: According to the ISO 527-3 standard, the test was carried out using a 3344 type material testing machine of Instron Corporation. The processing software was Bluehill version 2.31. The film was cut into Type 5 according to the ISO 527-3 standard parallel and perpendicular to the stretching direction (MD and CD) respectively, and placed in a Bluepard BPS–100CB constant temperature and humidity chamber (temperature 23 °C, relative humidity 50%) of Shanghai Yiheng Scientific Instrument Co., Ltd. for 24 hours. During the test, the initial fixture spacing was 75 mm, the test stretching rate was 100 mm / min, and each sample was tested at least 5 times, and the average value was taken.

[0104]

Example 1

[0105] Ethylene-vinyl alcohol copolymer (EVOH) was purchased from Kuraray Co., Ltd. in Japan, with the grade of EVAL TM H171B, and the ethylene content was 38 mol%; the melt flow rate at 190 °C / 2.16 kg was 1.7 g / 10 min.

[0106] 100 parts by weight of glycolide (GA), 0.1 part by weight of stannous octoate, 0.015 part by weight of ethylene-vinyl alcohol copolymer (EVOH), 0.035 part by weight of 1,4-butanediol, 0.3 part by weight of antioxidant 1010, and 0.6 part by weight of antioxidant 626 were uniformly mixed and then extruded and pelletized using a Labtech parallel co-rotating twin-screw extruder (screw diameter: 20 mm, length-diameter ratio: 40). The extruder has a total of 11 sections from the feed port to the die, numbered 1-11, where the first section only serves to feed materials and cannot be heated. The temperatures of the 2-11 sections of the extruder are respectively: 160 °C, 200 °C, 220 °C, 220 °C, 220 °C, 220 °C, 220 °C, 230 °C, 235 °C, and 240 °C. The feeding speed is 3 kg / h, and the screw speed is 150 rpm.

[0107] The product of Example 1 was detected by GPC, and its GPC spectrum showed a bimodal peak:

[0108] The high molecular weight peak corresponds to the polyglycolic acid graft copolymer, with a number average molecular weight of 1,805,926, a weight average molecular weight of 2,011,475, a molecular weight distribution of 1.11, and a mass fraction of 7.42%; the mass fraction of each was calculated from the ratio of the integral area of the high molecular weight peak on the GPC curve to the total integral area of the two peaks.

[0109] The low molecular weight peak corresponds to the polyglycolic acid homopolymer, with a number average molecular weight of 124,956, a weight average molecular weight of 199,216, a molecular weight distribution of 1.59, and a mass fraction of 92.58%. The mass fraction of each was calculated from the ratio of the integral area of the low molecular weight peak on the GPC curve to the total integral area of the two peaks.

[0110] The overall number average molecular weight of the product is 128,236, the weight average molecular weight is 268,237, and the molecular weight distribution is 2.09.

[0111] The melt flow rate (MFR) of the polyglycolic acid mixture prepared in Example 1 at 230 °C / 2.16 kg was 5.43 g / 10 min.

[0112]

Example 2

[0113] The ethylene-vinyl alcohol copolymer (EVOH) was purchased from Kuraray Co., Ltd., Japan, with the trade name EVAL TM H171B, with an ethylene content of 38 mol%; the melt flow rate at 190 °C / 2.16 kg was 1.7 g / 10 min.

[0114] 100 parts by weight of glycolide (GA), 0.1 part by weight of stannous octoate, 0.02 part by weight of ethylene-vinyl alcohol copolymer (EVOH), 0.04 part by weight of 1,4-butanediol, 0.5 part by weight of antioxidant 1010 and 0.5 part by weight of antioxidant 626 were mixed evenly and then extruded and pelletized using a Labtech parallel co-rotating twin-screw extruder (screw diameter: 20 mm, length-diameter ratio: 40). The extruder has a total of 11 sections from the feed port to the die, numbered 1-11, where the first section only serves to feed materials and cannot be heated. The temperatures of the 2-11 sections of the extruder are: 160 °C, 200 °C, 220 °C, 220 °C, 220 °C, 220 °C, 220 °C, 220 °C, 220 °C and 220 °C respectively. The feeding speed is 3 kg / h and the screw speed is 150 rpm.

[0115] The product of Example 2 was detected by GPC, and its GPC spectrum showed a bimodal peak:

[0116] The high molecular weight peak corresponds to the polyglycolic acid graft copolymer, with a number average molecular weight of 3308919, a weight average molecular weight of 4495149, a molecular weight distribution of 1.35, and its mass fraction is 6.06%; its respective mass fraction was calculated from the ratio of the integral area of this high molecular weight peak on the GPC curve to the total integral area of the two peaks.

[0117] The low molecular weight peak corresponds to the polyglycolic acid homopolymer, with a number average molecular weight of 66870, a weight average molecular weight of 190679, a molecular weight distribution of 2.85, and its mass fraction is 93.94%. Its respective mass fraction was calculated from the ratio of the integral area of this low molecular weight peak on the GPC curve to the total integral area of the two peaks.

[0118] The overall number average molecular weight of the product is 109481, the weight average molecular weight is 375278, and the molecular weight distribution is 3.43. The melt flow rate (MFR) of the polyglycolic acid mixture prepared in Example 2 at 230 °C / 2.16 kg was 4.31 g / 10 min.

[0119]

Example 3

[0120] In the ZE25Ax56D-UTX 1 co-rotating twin-screw extruder (screw diameter 25 mm, L / D = 56) of Krauss Maffei Germany, pelletizing of the degradable resin was carried out. 10 parts by weight of the polyglycolic acid mixture prepared in Example 2 was melt-blended and modified with 90 parts by weight of polybutylene adipate / terephthalate (PBAT), additives and other materials to prepare degradable resin particles. PBAT was purchased from BASF (melt index 3.5 g / 10 min), grade F Blend C1200. PGA was purchased from Corbion (M w:180000g / mol). The specific preparation process is as follows:

[0121] According to the total weight of the polyglycolic acid mixture and PBAT blended particles as 100 parts, 7 parts of nucleating agent talc (Kain Chemical), 0.5 parts of epoxy chain extender styrene-methyl methacrylate-glycidyl methacrylate (ADR, BASF), 0.2 parts of anti-blocking agent erucic acid amide (Jiangxi Zhilian Plastic Technology Co., Ltd.), 0.5 parts of antioxidant tetrakis [β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol ester (1010, BASF), 0.5 parts of light stabilizer bis (2,2,6,6-tetramethyl-4-piperidinyl) sebacate (770, BASF), 0.5 parts of ultraviolet light absorber 2-hydroxy-4-octyloxybenzophenone (UV531, BASF), 0.5 parts of anti-hydrolysis agent N,N'-bis (2,6-diisopropylphenyl) carbodiimide (Hymax 1010, Shanghai Langyi), prepared into about 2 kg of mixed powder additive.

[0122] 90 parts by mass of PBAT and 10 parts of grafted PGA are added to the extruder through different pellet feeders 1 and pellet feeder 2 of the extruder, and the mixed powder additive is added to the extruder through another powder feeder 3. The extruder has 11 sections from the feed port to the die, numbered 1-11, of which the first section only serves to add materials and cannot be heated. The temperatures of sections 2-11 of the extruder are 160°C, 200°C, 220°C, 220°C, 230°C, 230°C, 230°C, 230°C, 220°C and 220°C, respectively, and the screw speed is set at 250rpm. The mixed powder is fed to the first section of the twin-screw extruder with a loss-in-weight feeder provided by the extruder, and the feeding rate is: PBAT 15kg / h, mixed powder additive 1.46kg / h, polyglycolic acid mixture 1.87kg / h.

[0123] After stable operation, the twin-screw extruder has a pressure of 15-21 bar and a torque of 41-53%. The die of the extruder has two circular outlets with a diameter of 4 mm. After the strips are extruded from the die, they pass through a water bath cooling tank and are cut into cylindrical particles with a length of about 5 mm by a pelletizer. After vacuuming in a vacuum drying oven at 70°C for 4 hours, the biodegradable resin particles are obtained and collected and packaged for later use.

[0124] [Example 4] Preparation of degradable resin

[0125] In the ZE25Ax56D-UTX of Krauss Maffei in Germany 1Granulation of degradable resin is carried out in a co-rotating twin-screw extruder (screw diameter 25 mm, L / D = 56). 80 parts by mass of PBAT and 20 parts of the polyglycolic acid mixture prepared in Example 2 are added to the extruder through different pellet feeders 1 and 2 of the extruder. The screw processing conditions and the ratio of additive powder are controlled to be the same as those in Example 3. The feeding speeds are: 15 kg / h for PBAT, 1.81 kg / h for the mixed powder additive, and 3.75 kg / h for the polyglycolic acid mixture.

[0126] After stable operation, the pressure of twin-screw extrusion is 15 - 21 bar and the torque is 40 - 50%. There are two circular outlets with a diameter of 4 mm each on the die equipped with this extruder. After the sample strip is extruded from the die, it passes through a water bath cooling tank and is cut into cylindrical particles with a length of about 5 mm by a pelletizer. After vacuumizing for 4 hours in a 70 °C vacuum drying oven, degradable resin particles are obtained and collected and sealed for standby.

[0127]

Example 5

[0128] In the ZE25Ax56D-UTX co-rotating twin-screw extruder of Krauss Maffei Company in Germany 1 Granulation of degradable resin is carried out in a co-rotating twin-screw extruder (screw diameter 25 mm, L / D = 56). 75 parts by mass of PBAT and 25 parts of the polyglycolic acid mixture prepared in Example 2 are added to the extruder through different pellet feeders 1 and 2 of the extruder. The screw processing conditions and the ratio of additive powder are controlled to be the same as those in Example 3. The feeding speeds are: 15 kg / h for PBAT, 1.94 kg / h for the mixed powder additive, and 5 kg / h for the polyglycolic acid mixture.

[0129] After stable operation, the pressure of twin-screw extrusion is 16 - 21 bar and the torque is 45 - 51%. There are two circular outlets with a diameter of 4 mm each on the die equipped with this extruder. After the sample strip is extruded from the die, it passes through a water bath cooling tank and is cut into cylindrical particles with a length of about 5 mm by a pelletizer. After vacuumizing for 4 hours in a 70 °C vacuum drying oven, degradable resin particles are obtained and collected and sealed for standby.

[0130]

Example 6

[0131] In the ZE25Ax56D-UTX co-rotating twin-screw extruder of Krauss Maffei Company in Germany 1Pelletizing of degradable resin is carried out in a co-rotating twin-screw extruder (screw diameter 25 mm, L / D = 56). 70 parts by mass of PBAT and 30 parts by mass of the polyglycolic acid mixture of Example 1 are added to the extruder through different pellet feeders 1 and 2 of the extruder. The screw processing conditions and the ratio of additive powder are controlled to be the same as those in Example 3. The feeding speeds are: PBAT 15 kg / h, mixed powder additive 2.08 kg / h, and polyglycolic acid mixture 6.42 kg / h.

[0132] After stable operation, the pressure of twin-screw extrusion is 17 - 21 bar and the torque is 45 - 51%. The die equipped with this extruder has two circular outlets with a diameter of 4 mm each. After the sample strips are extruded from the die, they pass through a water bath cooling tank and are cut into cylindrical particles with a length of about 5 mm by a pelletizer. After being vacuumed for 4 hours in a 70 °C vacuum drying oven, degradable resin particles are obtained and collected and sealed for standby.

[0133]

Comparative Example 1

[0134] Pelletizing is carried out in a co-rotating twin-screw extruder (screw diameter 25 mm, L / D = 56) of Krauss Maffei Germany's ZE25Ax56D-UTX 1 80 parts by mass of PBAT and 20 parts by mass of commercially available homopolymer PGA (purchased from Shanghai Boli, Mw = 180000 g / mol) are added to the extruder through different pellet feeders 1 and 2 of the extruder. The screw processing conditions and the ratio of additive powder are controlled to be the same as those in Example 4. The feeding speeds are: PBAT 15 kg / h, mixed powder additive 1.81 kg / h, and commercially available homopolymer PGA 3.75 kg / h.

[0135] After stable operation, the pressure of twin-screw extrusion is 15 - 17 bar and the torque is 40 - 45%. The die equipped with this extruder has two circular outlets with a diameter of 4 mm each. After the sample strips are extruded from the die, they pass through a water bath cooling tank and are cut into cylindrical particles with a length of about 5 mm by a pelletizer. After being vacuumed for 4 hours in a 70 °C vacuum drying oven, degradable resin particles are obtained and collected and sealed for standby.

[0136]

Comparative Example 2

[0137] In Krauss Maffei Germany's ZE25Ax56D-UTX 1Pelletizing was carried out in a co-rotating twin-screw extruder (screw diameter 25 mm, L / D = 56). 70 parts by mass of PBAT and 30 parts by mass of commercially available homopolymeric PGA were added to the extruder through different pellet feeders 1 and pellet feeder 2 of the extruder. The commercially available homopolymeric PGA was purchased from Shanghai Boli (Mw = 180,000 g / mol). The screw processing conditions and the ratio of additive powder were the same as those in Example 4. The feeding speeds were: PBAT 15 kg / h, mixed powder 2.08 kg / h, and commercially available homopolymeric PGA 6.42 kg / h.

[0138] After stable operation, the pressure of the twin-screw extrusion was 14 - 17 bar and the torque was 40 - 45%. The die equipped with this extruder had two circular outlets with a diameter of 4 mm each. After the sample strips were extruded from the die, they passed through a water bath cooling tank and were cut into cylindrical particles with a length of about 5 mm by a pelletizer. After being evacuated in a vacuum drying oven at 70°C for 4 hours, degradable resin particles were obtained and collected and stored for later use.

[0139]

Example 7

[0140] The degradable resins obtained in Examples 4 - 6 and Comparative Examples 1 - 2 above were subjected to differential scanning calorimetry (DSC) tests. The crystallization temperature (T c ) and crystallization enthalpy (△H c ) during the cooling process, as well as the melting temperature (T m ) and melting enthalpy (△H m ) during the second heating process are shown in Table 1.

[0141] Table 1. DSC test results of Examples 4 - 6 and Comparative Examples 1 - 2 (cooling process and second heating process)

[0142]

[0143] As Figure 1 and Table 1 show, comparing Example 4 with Comparative Example 1, compared with adding homopolymeric PGA: (1) In the first heating curve in Figure 1 , the second melting peak (T m2 ) of the blended particles in Example 4 was wider than that of the blended particles in Comparative Example 1. This also made it easier for PGA to melt and crystallize and orient during the low-temperature blown film process, thus improving its mechanical properties. (2) After adding the polyglycolic acid mixture, the crystallization enthalpy of PBAT was greater, and the crystallization peak temperature T m1 of PBAT was higher (123.7°C) during the second heating process (as shown in Table 1). This indicates that after adding the polyglycolic acid mixture, the crystallization process of PBAT can be effectively promoted; in addition, as Figure 2 shows, during the second heating process, the melting peak T of PGA in Example 4m2 It no longer appears, indicating that PGA in Example 4 exists more in an amorphous state and the film toughness is better.

[0144] like Figure 3 As shown in Table 3, when comparing the first heating process, Example 6 and Comparative Example 2, under the condition of adding a higher proportion of PGA mixture (30%), the melting enthalpy of PGA in Example 6 is significantly smaller than that in Comparative Example 2, indicating that the grafted PGA mixture has better compatibility with PBAT than the homopolymerized PGA. As shown in Table 3, during the cooling process, there is no T in Example 6. c1 This indicates that the crystallization of PGA in Example 6 is significantly slower, and there is no time for crystallization during the rapid cooling process. However, more crystallization in Comparative Example 2 will cause the film to break easily during the film blowing process, affecting the stability of the film blowing.

[0145] [Example 8] Preparation of degradable mulch film

[0146] The degradable resins obtained in Examples 3 to 6 and Comparative Examples 1 to 2 were placed in HAAKE TM Rheomex OS single screw extruder blown film, the extruder screw diameter is 19mm, the aspect ratio is 25, equipped with 3:1 standard metering screw, the single screw extruder is manufactured by HAAKE TM PolyLab TM OS torque rheometer platform control. The extruder has four heating sections, numbered 1-4 from the feed port to the outlet, and is equipped with a blown film die with a heating function, a die diameter of 19.5mm, a die gap of 0.5mm, and a screw speed of 50rpm. The temperatures of each section are shown in Table 2. Subsequently, the degradable mulch film is made through cooling, shaping, stretching, and winding. The thickness is controlled to be around 9μm. The specific processing parameters and thickness are shown in Table 2.

[0147] Table 2. Film blowing processing conditions for ground film

[0148]

[0149]

[0150] [Example 9] Test on mechanical properties of ground film

[0151] The ground film prepared in Example 8 was tested for tensile properties of the film strips in parallel to the stretching direction (MD) and perpendicular to the film blowing direction (CD) according to the test steps described above. The results are shown in Table 3. Figure 4 , Figure 5 , Figure 6 .

[0152] Table 3. Mechanical property results of different plastic films

[0153]

[0154] As Figures 4 - 5 shown in Table 3, at a lower film blowing temperature, due to the wider molecular weight distribution of the polyglycolic acid mixture, it is easier to crystallize as a whole, and a small amount of oligomers, which can act as compatibilizers, increase the compatibility between PGA and PBAT. Therefore, compared with the homopolymeric PGA / PBAT plastic films in Comparative Examples 1 and 2, the overall mechanical strength of the plastic films prepared from the degradable resins in Examples 3 to 6 (especially Examples 4 to 6) is better.

[0155] As Figure 6 shown in Table 3, at a higher film blowing temperature of 220 °C, the mechanical properties of the plastic film prepared from the degradable resin obtained in Example 4 are also significantly better than those of the plastic film prepared from the degradable resin in Comparative Example 1. This shows that the plastic film in the present invention can achieve a good PGA / PBAT strengthening effect at a relatively wide film blowing temperature range (190 - 220 °C).

[0156] In the present invention, the polyglycolic acid mixture can not only significantly improve the mechanical properties of the obtained plastic film during high-temperature film blowing, but also the film obtained in Example 4 still has good mechanical properties at a low temperature (190 °C) film blowing and meets the national standard GB / T - 35795. However, when using homopolymeric PGA for film blowing at 190 °C, the performance is poor and does not meet the national standard GB / T - 35795. It can be seen that using the polyglycolic acid mixture described in the present invention as a plastic film strengthening material can significantly broaden the processing temperature of PGA plastic films. Under the condition of low-temperature film blowing, the degradable plastic film prepared from the degradable resin described in the present invention can not only meet the mechanical property requirements, but also greatly improve the opening property, effectively enhancing the processing stability of the industrial scale-up of PGA plastic films.

[0157] The present invention has been described in detail above in combination with specific embodiments and exemplary examples, but these descriptions should not be construed as limiting the present invention. Those skilled in the art understand that without departing from the spirit and scope of the present invention, various equivalent substitutions, modifications or improvements can be made to the technical solutions of the present invention and their implementation manners, and all of these fall within the scope of the present invention. The protection scope of the present invention is subject to the appended claims.

Claims

1. A degradable resin capable of film blowing at low temperature, which comprises a mixture of a degradable polyester and polyglycolic acid, and the polyglycolic acid mixture comprises a polyglycolic acid graft copolymer and a polyglycolic acid homopolymer; Wherein, The polyglycolic acid graft copolymer has a polyolefin as the main chain, and polyglycolic acid side chains are grafted on the main chain.

2. The degradable resin according to claim 1, Characterized in that, The degradable polyester is selected from a degradable polyester homopolymer and / or a degradable polyester copolymer, preferably at least one of the homopolymers of polybutylene adipate / terephthalate, poly(butylene succinate / butylene terephthalate), polylactic acid, polycaprolactone, polypropylene carbonate, polybutylene succinate, and polyhydroxyalkanoate; and / or, Based on 100 wt% of the polyglycolic acid mixture, the content of the polyglycolic acid graft copolymer is 0.1 wt% to 80 wt%, and the content of the polyglycolic acid homopolymer is 20 wt% to 99.9 wt%.

3. The degradable resin according to claim 1, Characterized in that, The weight average molecular weight of the polyglycolic acid mixture is 150,000 to 1,200,000 g / mol, preferably 200,000 to 400,000 g / mol; and / or, The weight average molecular weight of the polyglycolic acid graft copolymer in the polyglycolic acid mixture is 500,000 to 10,000,000 g / mol, preferably 1,000,000 to 6,000,000 g / mol; and / or, The weight average molecular weight of the polyglycolic acid homopolymer in the polyglycolic acid mixture is 50,000 to 350,000 g / mol, preferably 100,000 to 200,000 g / mol.

4. The degradable resin according to claim 1, Characterized in that, Based on the total weight of the degradable polyester and the polyglycolic acid mixture being 100 parts by weight, the degradable polyester is 60 to 95 parts, and the polyglycolic acid mixture is 5 to 40 parts; preferably, based on the total weight of the degradable polyester and the polyglycolic acid mixture being 100 parts by weight, the degradable polyester is 65 to 95 parts, and the polyglycolic acid mixture is 5 to 35 parts.

5. The degradable resin according to any one of claims 1 to 4, Characterized in that, The degradable resin further comprises an additive; preferably, based on the total weight of the degradable polyester and the polyglycolic acid mixture being 100 parts, the additive is 0.08 to 76 parts, preferably 1 to 47 parts.

6. The degradable resin according to claim 5, Characterized in that, The additive is selected from at least one of a nucleating agent, a chain extender, an antiblocking agent, and a stabilizer; Preferably, based on the total weight of the degradable polyester and the polyglycolic acid mixture being 100 parts, the nucleating agent is 0.02 to 30 parts, the chain extender is 0.01 to 6 parts, the antiblocking agent is 0.02 to 10 parts, and the stabilizer is 0.03 to 30 parts.

7. A method for preparing a degradable resin capable of film blowing at low temperature, preferably for preparing the degradable resin according to any one of claims 1 to 6, the preparation method Comprises: Mixing components including the degradable polyester, the polyglycolic acid mixture and optionally an additive, and melt-extruding and pelletizing to obtain the degradable resin.

8. The preparation method according to claim 7, wherein, the preparation method includes: (1) mixing the optional auxiliary agent to obtain an auxiliary agent mixture; (2) mixing the biodegradable polyester and the polyglycolic acid mixture, and optionally adding the auxiliary agent mixture; (3) melt-extruding, cooling, and pelletizing to obtain the biodegradable resin; preferably, the temperature of the melt-extrusion is 50-350°C, preferably 50-300°C.

9. The preparation method according to claim 8, wherein, the polyglycolic acid mixture is obtained as follows: polymerizing materials including a polyolefin with a hydroxyl side group, a homopolymer polyglycolic acid initiator, a polyglycolic acid monomer, and a catalyst; preferably: the polyolefin with a hydroxyl side group is selected from at least one of ethylene-vinyl alcohol copolymer and polyvinyl alcohol homopolymer; and / or, the polyglycolic acid monomer is selected from at least one of glycolide and glycolic acid; and / or, the homopolymer polyglycolic acid initiator is selected from at least one of a monohydric alcohol, a polyhydric alcohol, and an amine compound, preferably at least one of a monohydric alcohol, a polyhydric alcohol, and an amine compound with a boiling point higher than 160°C; and / or, the catalyst is selected from at least one of salt compounds and organic guanidine compounds corresponding to one or more elements among the metal elements of Group IIA, IIIA, IVA, VA, IVB, VIIB, VIII, and IIB, preferably at least one of Sn salts, Bi salts, Mg salts, Al salts, Ca salts, Fe salts, Mn salts, Ti salts, and Zn salts; more preferably, the weight ratio of the polyglycolic acid monomer to the polyolefin with a hydroxyl side group is 100:(0.001-10), preferably 100:(0.01-1); and / or, the weight ratio of the polyglycolic acid monomer to the homopolymer polyglycolic acid initiator is 100:(0.001-10), preferably 100:(0.01-1); and / or, the weight ratio of the polyglycolic acid monomer to the catalyst is 100:(0.005-1), preferably 100:(0.01-0.2).

10. An ultrathin, high-strength, and easy-to-open biodegradable film, which is prepared from the biodegradable resin capable of blown film at low temperature according to any one of claims 1-6; preferably obtained by blown film.

11. A preparation method of an ultrathin, high-strength, and easy-to-open biodegradable film, preferably used for preparing the biodegradable film according to claim 10, the preparation method includes: melt-extruding, blown film, and cooling the biodegradable resin according to any one of claims 1-6 to obtain the biodegradable film.

12. Application of the biodegradable film according to claim 10 or the biodegradable film obtained by using the preparation method according to claim 11 in biodegradable ground films.

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