Method for preparing PLA-PCL polyester copolymer for biomass pressure-sensitive adhesive under non-catalytic condition

Abstract

The invention discloses a method for preparing a PLA-PCL polyester copolymer for a biomass pressure-sensitive adhesive under a non-catalytic condition, which comprises the following steps: S1, putting L-LA and epsilon-CL into a reaction container, adding ethylene glycol or glycerol into the reaction container, and subsequently carrying out argon protection treatment; s2, heating the reaction container containing the sample at 180-240 DEG C for 3 hours; and S3, after the reaction, forming a uniform system, namely obtaining the PLA-PCL polyester copolymer for the biomass pressure-sensitive adhesive. According to the preparation method, L-LA and epsilon-CL are taken as raw materials, an alcohol compound is taken as an initiator, and the PLA-PCL polyester copolymer for the biomass pressure-sensitive adhesive is directly prepared through reaction at high temperature. The method has the beneficial effects that no catalyst is needed in the reaction process, the process method is simple and convenient, and the preparation process is short in time consumption; the prepared product can be used for preparing a biomass pressure-sensitive adhesive.

Description

Technical Field

[0001] The invention relates to the technical field of pressure-sensitive adhesives, and in particular to a method for preparing a PLA-PCL polyester copolymer for biomass pressure-sensitive adhesives under non-catalytic conditions. Background Art

[0002] Pressure-sensitive adhesive (PSA) is a type of adhesive that is sensitive to pressure and can adhere to various substrates with only a small external force. It has both the viscous properties of a liquid and the elastic properties of a solid. When the pressure-sensitive adhesive is spread on the rough surface of the substrate, due to the wettability and plasticity of the pressure-sensitive adhesive itself, it can increase the contact area between the adhesive and the adherend, forming a strong bond. Because bio-based pressure-sensitive adhesives have good biocompatibility and biodegradability, they are widely used in the medical field. They can also be used in electronics, automobiles, aviation, ships and other fields, making important contributions to achieving sustainable development.

[0003] In recent years, with the expansion of demand for packaging, decoration, office supplies and various labels, people's demand for pressure-sensitive adhesives has also increased. Acrylic pressure-sensitive adhesive emulsions have become the development direction of pressure-sensitive adhesives and have been widely used because they are non-toxic, non-polluting, and have excellent aging resistance, weather resistance, pressure sensitivity and adhesion. In view of the characteristics of pressure-sensitive adhesives that are easy to stick, easy to peel, not damaged, and will not dry up for a long time, while selecting the main monomer and second monomer of acrylic esters, a variety of functional group monomers are introduced. Through repeated experiments and reasonable adjustment of process formulas, a multi-copolymer acrylic ester pressure-sensitive adhesive emulsion with good comprehensive performance is screened and synthesized, which can be used in the production of double-sided tapes, trademark papers, etc. that require transfer coating processes. In addition, acrylic pressure-sensitive tapes, double-sided tapes, protective tapes, masking tapes, label tapes, and medical tapes have not only greatly improved in production, but also in bonding and coating performance, and tape products suitable for various purposes continue to emerge. Despite this, the acrylic pressure-sensitive adhesive and tape industry is still dominated by general-purpose products with a single variety. In addition, it cannot meet the needs of the market in terms of bonding performance, water resistance, heat resistance and moisture resistance. Special tapes still need to be imported. Such as high-strength double-sided tape, high-temperature resistant masking tape, flame-retardant tape, magic tape, solar film and marking tape, etc. Through the use of various modification methods, the development of polyacrylate emulsion pressure-sensitive adhesive is changing with each passing day. With the synthesis of various new acrylic ester monomers, the components with special functions are introduced into the polyacrylate emulsion pressure-sensitive adhesive system to obtain products with different properties, which will surely broaden its application field and make it develop in the direction of functionalization and diversification.

[0004] Since pressure-sensitive adhesive is a high-molecular cross-linked material with a complex internal structure, it is not easily degraded by the environment. After being discarded, it can only be landfilled or incinerated, causing pollution to the environment.

[0005] In the prior art:

[0006] A Chinese patent with publication number CN107177339A discloses a biodegradable lactide oligomer adhesive, which is obtained by polymerization of lactide. However, a solvent is used in the preparation process, and the environmental friendliness is poor.

[0007] Chinese patent publication number CN1288033A discloses a method for preparing a water-soluble biodegradable adhesive from a mixture of polyaspartic acid, its salts and derivatives and a natural thickener resin, but this method has a complex process and high cost.

[0008] Therefore, there is an urgent need for a green, environmentally friendly, fully degradable biomass pressure-sensitive adhesive with a simple preparation process to meet the demand. Summary of the invention

[0009] The purpose of the present invention is to provide a method for preparing a PLA-PCL polyester copolymer for biomass pressure-sensitive adhesive under non-catalytic conditions.

[0010] To achieve the above object, the present invention is implemented by the following technical solutions:

[0011] A method for preparing a PLA-PCL polyester copolymer for a biomass pressure-sensitive adhesive under non-catalytic conditions, the preparation method comprising: using L-lactide and ε-caprolactone as monomers, an alcohol compound as an initiator, and directly preparing the PLA-PCL polyester copolymer for a biomass pressure-sensitive adhesive by heating;

[0012] The specific steps are as follows:

[0013] (1) adding alcohol compounds to L-LA and ε-CL;

[0014] (2) heating the reaction at a temperature of 100° C. to 400° C. for a reaction time of 9 h to 36 h;

[0015] (3) After the reaction, the obtained product becomes a uniform system, that is, the PLA-PCL polyester copolymer for biomass pressure-sensitive adhesive is obtained;

[0016] Among them, L-lactide is L-LA; ε-caprolactone is ε-CL;

[0017] The mass ratio of the alcohol compound to L-LA and ε-CL is 1:(1-100):(1-10).

[0018] As a further improvement of this scheme,

[0019] The chemical formula of the alcohol compound is shown in formula (I):

[0020]

[0021] In formula (I), R1 is an alkyl group, and n is 1-4;

[0022] The chemical formula of the L-LA is shown in formula (II):

[0023]

[0024] The chemical formula of the ε-CL is shown in formula (III):

[0025]

[0026] As a further improvement of this scheme,

[0027] The alcohol compound is a type of organic compound generated by replacing one or several hydrogen atoms in a hydrocarbon molecule with a hydroxyl group.

[0028] As a further improvement of this scheme,

[0029] The alcohol compound is any one or more of ethylene glycol and propylene glycol.

[0030] As a further improvement of this scheme,

[0031] In step (1), the mass ratio of the alcohol compound to L-LA and ε-CL is 1:(1-20):(3-8).

[0032] As a further improvement of this scheme,

[0033] The reaction processes of step (1) and step (2) are all carried out under an inert atmosphere.

[0034] As a further improvement of this scheme,

[0035] In step (2), the reaction temperature is 100°C to 240°C

[0036] The reaction time is 9h to 15h.

[0037] The method for preparing PLA-PCL polyester copolymer for biomass pressure-sensitive adhesive under non-catalytic conditions of the present invention has the following beneficial effects:

[0038] 1. The present invention uses L-LA and ε-CL as raw materials, alcohol compounds as initiators, and no catalyst is required to directly prepare PLA-PCL polyester copolymer for biomass pressure-sensitive adhesive at high temperature;

[0039] 2. The invention has a simple formula, does not require a catalyst in the reaction process, has a simple process, and takes a short preparation time, which provides a new research direction and research method for the preparation of bio-based pressure-sensitive adhesives. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Schematic diagram of the synthesis of PLA-PCL polyester copolymers in Examples 1 and 2;

[0041] Figure 2 is a gel permeation chromatogram of the PLA-PCL polyester copolymer synthesized in Example 1;

[0042] Figure 3 IR spectra of L-LA, ε-CL and synthesized PLA-PCL polyester copolymer in Example 1;

[0043] Figure 4 1H and 13C NMR spectra of the PLA-PCL polyester copolymer synthesized in Example 2;

[0044] Figure 5 is a gel permeation chromatogram of the PLA-PCL polyester copolymer synthesized in Example 2;

[0045] Figure 6 is a gel permeation chromatogram of the PLA-PCL polyester copolymer synthesized in Example 6;

[0046] Figure 7 is a gel permeation chromatogram of the PLA-PCL polyester copolymer synthesized in Example 7;

[0047] Figure 8 is the DSC spectrum of the PLA-PCL polyester copolymer synthesized in Example 2;

[0048] Fig. 9 This is the DSC spectrum of the PLA-PCL polyester copolymer synthesized in Example 1. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solutions and advantages of the present invention more clear, the following embodiments and the accompanying drawings are combined to illustrate the present invention. Figures 1 to 8 The present invention will be further described:

[0050] Example 1

[0051] The invention discloses a method for preparing a PLA-PCL polyester copolymer for biomass pressure-sensitive adhesive by using L-LA and ε-CL as raw materials and glycerol as an initiator.

[0052] First, take 0.4 ml of ε-CL and 0.14 g of L-LA in a reaction container, mix ε-CL and L-LA with propylene glycol in a mass ratio of 10:2:1, then evacuate the reaction system, and then introduce argon protection, and repeat this operation three times.

[0053] The reaction system was treated at 170°C for 3 h, 180°C for 3 h, 190°C for 3 h, and finally at 200°C for 3 h. The reaction product was in a clear, colorless, transparent state and had a certain viscosity, and the reactants became a uniform system.

[0054] Isocyanate (MDI) and commercial terminal hydroxyl saturated polyester resin were dissolved and reacted to prepare a long-chain crosslinking agent, which was then mixed with the reaction product in Example 1, wherein the mass ratio of the reaction product to the commercial terminal hydroxyl saturated polyester resin (including MDI) was 0.8:0.2. The formed product was coated on a PET film with a thickness of 25 um, and the film was placed in an oven for curing at 100°C for 1 min. After the film was taken out, it was found to have relatively good viscosity.

[0055] Table 1 Pressure-sensitive adhesive a prepared by the reaction product in Example 1 of the present invention is tested for its performance

[0056] Steel plate / gf / 25mm PET board / gf / 25mm PVC board / gf / 25mm Pressure sensitive adhesive 42.502 49.135 56.665

[0057] Figure 2 This is the gel permeation chromatogram of the PLA-PCL polyester copolymer synthesized under the above conditions.

[0058] As can be seen from the figure, there is only one peak, indicating that ε-CL and L-LA have reacted to form the target product.

[0059] Among them, Mn=4953, Mw=7193, Mz=9944, Mw / Mn=1.45.

[0060] The number average molecular weight of the product in this example is relatively large, and it is speculated that it can be used to prepare a pressure-sensitive adhesive.

[0061] Figure 3 Infrared spectra of L-LA, ε-CL and synthesized PLA-PCL polyester copolymer.

[0062] Figure a is the infrared spectrum of ε-CL.

[0063] Figure b is the infrared spectrum of L-LA.

[0064] Figure c is the infrared spectrum of the synthesized PLA-PCL polyester copolymer.

[0065] The ester bond absorption peak is at 1730 cm-1 in the figure, indicating that ε-CL and L-LA have reacted to form the target product.

[0066] Fig. 9 This is the DSC spectrum of the PLA-PCL polyester copolymer synthesized under the above conditions.

[0067] It can be seen that no melting point was found in the product.

[0068] Example 2

[0069] The invention discloses a method for preparing a PLA-PCL polyester copolymer for biomass pressure-sensitive adhesive by using L-LA and ε-CL as raw materials and glycerol as an initiator.

[0070] First, take 0.4 ml of ε-CL and 0.14 g of L-LA in a reaction container, mix ε-CL and L-LA with ethylene glycol in a mass ratio of 10:2:1, then evacuate the reaction system, and then introduce argon protection, and repeat this operation three times.

[0071] The reaction system was treated at 170°C for 3 h, 180°C for 3 h, 190°C for 3 h, and finally at 200°C for 3 h. The reaction product was in a clear, colorless, transparent state and had a certain viscosity and very low fluidity, and the reactants became a homogeneous system.

[0072] Isocyanate (MDI) and commercial terminal hydroxyl saturated polyester resin were dissolved and reacted to prepare a long-chain crosslinking agent, which was then mixed with the reaction product in Example 1, wherein the mass ratio of the reaction product to the commercial terminal hydroxyl saturated polyester resin (including MDI) was 0.8:0.2. The formed product was coated on a PET film with a thickness of 25 um, and the film was placed in an oven for curing at 100°C for 1 min. After the film was taken out and bonded, it was found that the viscosity was lower than the pressure-sensitive adhesive prepared in Example 1.

[0073] Table 2 Performance test of pressure-sensitive adhesive b obtained from the reaction product in Example 2 of the present invention

[0074] Steel plate / gf / 25mm PET board / gf / 25mm PVC board / gf / 25mm Pressure sensitive adhesive 11.433 22.336 26.443

[0075] Figure 4 1H and 13C NMR spectra of PLA-PCL polyester copolymer synthesized under the above conditions.

[0076] In the 1H NMR spectrum, the signal appearing at δ = 4.21 ppm corresponds to the characteristic proton peak of CH2-OC=O in ethylene glycol, and the proton resonance peak of CH3-CH-OC=O appears at δ = 5.19 ppm, indicating the formation of long polyester chains.

[0077] In the 13C NMR spectrum, a resonance peak corresponding to the carbon atom on CH2-OC=O appeared at δ=64.35 ppm, and resonance peaks corresponding to the carbon atom on the ester group O=CO appeared at δ=170.20 and 169.89 ppm, also indicating the formation of long polyester chains.

[0078] Figure 5This is the gel permeation chromatogram of the PLA-PCL polyester copolymer synthesized under the above conditions.

[0079] As can be seen from the figure, there is only one peak, indicating that ε-CL and L-LA have reacted to form the target product.

[0080] Among them, Mn=2495, Mw=3952, Mz=5797, Mw / Mn=1.58.

[0081] Compared with the PLA-PCL polyester copolymer synthesized in Example 1, the number average molecular weight of the product in this example is much lower than that of the product in Example 1. This is the essential reason for the reduction in viscosity strength during the preparation of the pressure-sensitive adhesive, which may be caused by different initiators.

[0082] Figure 8 This is the DSC spectrum of the PLA-PCL polyester copolymer synthesized under the above conditions.

[0083] It can be seen that the product has an endothermic peak and a melting point of 45°C.

[0084] Example 3

[0085] The invention discloses a method for preparing a PLA-PCL polyester copolymer for biomass pressure-sensitive adhesive by using L-LA and ε-CL as raw materials and glycerol as an initiator.

[0086] First, take 0.4 ml of ε-CL and 0.14 g of L-LA in a reaction container, mix ε-CL and L-LA with propylene glycol in a mass ratio of 10:2:1, then evacuate the reaction system, and then introduce argon protection, and repeat this operation three times.

[0087] The reaction system was treated at 170°C for 3h, 180°C for 3h, and finally, at 190°C for 3h. The reaction product was a clear, colorless, transparent uniform system, but the viscosity was slightly lower than that in Example 1 and had greater fluidity. The pressure-sensitive adhesive made using the product in this example was not ideal.

[0088] Example 4

[0089] The invention discloses a method for preparing a PLA-PCL polyester copolymer for biomass pressure-sensitive adhesive by using L-LA and ε-CL as raw materials and glycerol as an initiator.

[0090] First, take 0.4 ml of ε-CL and 0.14 g of L-LA in a reaction container, mix ε-CL and L-LA with propylene glycol in a mass ratio of 10:2:1, then evacuate the reaction system, and then introduce argon protection, and repeat this operation three times.

[0091] The reaction system was treated at 170°C for 3h, 180°C for 3h, 190°C for 3h, 200°C for 3h, and finally at 220°C for 3h. The reaction product was a clear, colorless, transparent uniform system, but compared with the product in Example 1, the viscosity was slightly reduced and the fluidity was greater. The pressure-sensitive adhesive made with the product in this example was also not ideal.

[0092] Example 5

[0093] The invention discloses a method for preparing a PLA-PCL polyester copolymer for biomass pressure-sensitive adhesive by using L-LA and ε-CL as raw materials and pentaerythritol as an initiator.

[0094] First, take 0.4 ml of ε-CL and 0.14 g of L-LA in a reaction container, mix ε-CL and L-LA with pentaerythritol in a mass ratio of 10:2:1, then evacuate the reaction system, and then introduce argon protection, and repeat this operation three times.

[0095] The reaction system was treated at 180°C for 3 h, 200°C for 3 h, 220°C for 3 h, and finally, at 240°C for 3 h, and the reactants became a uniform system.

[0096] Example 6

[0097] The invention discloses a method for preparing a PLA-PCL polyester copolymer for biomass pressure-sensitive adhesive by using L-LA and ε-CL as raw materials and glycerol as an initiator.

[0098] First, take 0.3 ml of ε-CL and 0.12 g of L-LA in a reaction container, mix ε-CL and L-LA with propylene glycol in a mass ratio of 11:3:1, then evacuate the reaction system, and then introduce argon protection, and repeat this operation three times.

[0099] The reaction system was treated at 180°C for 6 h, 190°C for 3 h, and finally, at 200°C for 3 h, and the reactants became a uniform system.

[0100] Figure 6 This is the gel permeation chromatogram of the PLA-PCL polyester copolymer synthesized under the above conditions.

[0101] As can be seen from the figure, there is only one peak, indicating that ε-CL and L-LA have reacted to form the target product.

[0102] Among them, Mn=3783, Mw=5186, Mz=6894, Mw / Mn=1.37.

[0103] Example 7

[0104] The invention discloses a method for preparing a PLA-PCL polyester copolymer for biomass pressure-sensitive adhesive by using L-LA and ε-CL as raw materials and ethylene glycol as an initiator.

[0105] First, take 0.3 ml of ε-CL and 0.12 g of L-LA in a reaction container, mix ε-CL and L-LA with ethylene glycol in a mass ratio of 11:2:1, then evacuate the reaction system, and then introduce argon protection, and repeat this operation three times.

[0106] The reaction system was treated at 190°C for 6 h and 200°C for 6 h, and the reactants became a uniform system.

[0107] Figure 7 This is the gel permeation chromatogram of the PLA-PCL polyester copolymer synthesized under the above conditions.

[0108] It can be seen from the figure that there is only one peak, indicating that ε-CL and L-LA have reacted to form the target product, where Mn = 3466, Mw = 4841, Mz = 6379, and Mw / Mn = 1.39.

[0109] Example 8

[0110] The invention discloses a method for preparing a PLA-PCL polyester copolymer for biomass pressure-sensitive adhesive by taking L-LA and ε-CL as raw materials and propylene glycol and ethylene glycol as initiators at the same time.

[0111] First, take 0.4 ml of ε-CL and 0.14 g of L-LA in a reaction container, mix ε-CL, L-LA, propylene glycol and ethylene glycol in a mass ratio of 10:2:1:1, then evacuate the reaction system, and then introduce argon protection, and repeat this operation three times.

[0112] The reaction system was treated at 180°C for 3 h, 190°C for 3 h, and finally, at 200°C for 3 h, and the reactants became a uniform system.

[0113] Example 9

[0114] The invention discloses a method for preparing PLA-PCL polyester copolymer for biomass pressure-sensitive adhesive by taking L-LA and ε-CL as raw materials and propylene glycol and pentaerythritol as initiators at the same time.

[0115] First, take 0.4 ml of ε-CL and 0.14 g of L-LA in a reaction container, mix ε-CL, L-LA, propylene glycol and pentaerythritol in a mass ratio of 10:2:1:1, then evacuate the reaction system, and then introduce argon protection, and repeat this operation three times.

[0116] The reaction system was treated at 180°C for 3 h, 190°C for 3 h, and finally, at 200°C for 2 h, and the reactants became a uniform system.

[0117] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent changes made using the present invention are within the patent protection scope of the present invention.

Claims

1. A method for preparing PLA-PCL polyester copolymer for biomass pressure-sensitive adhesive under non-catalytic conditions, characterized in that: The preparation method comprises the following steps: using L-lactide and ε-caprolactone as monomers, an alcohol compound as an initiator, and directly preparing a PLA-PCL polyester copolymer for biomass pressure-sensitive adhesive by heating; The specific steps are as follows: (1) adding alcohol compounds to L-LA and ε-CL; (2) heating the reaction at a temperature of 100° C. to 400° C. for a reaction time of 9 h to 36 h; (3) After the reaction, the obtained product becomes a uniform system, that is, the PLA-PCL polyester copolymer for biomass pressure-sensitive adhesive is obtained; Among them, L-lactide is L-LA; ε-caprolactone is ε-CL; The mass ratio of the alcohol compound to L-LA and ε-CL is 1:(1-100):(1-10).

2. The method for preparing PLA-PCL polyester copolymer for biomass pressure-sensitive adhesive under non-catalytic conditions according to claim 1, characterized in that: The chemical formula of the alcohol compound is shown in formula (I): In formula (I), R1 is an alkyl group, and n is 1-4; The chemical formula of the L-LA is shown in formula (II): The chemical formula of the ε-CL is shown in formula (III):

3. The method for preparing PLA-PCL polyester copolymer for biomass pressure-sensitive adhesive under non-catalytic conditions according to claim 1, characterized in that: The alcohol compound is a type of organic compound generated by replacing one or several hydrogen atoms in a hydrocarbon molecule with a hydroxyl group.

4. The method for preparing PLA-PCL polyester copolymer for biomass pressure-sensitive adhesive under non-catalytic conditions according to claim 1, characterized in that: The alcohol compound is any one or more of ethylene glycol and propylene glycol.

5. The method for preparing PLA-PCL polyester copolymer for biomass pressure-sensitive adhesive under non-catalytic conditions according to claim 1, characterized in that: In step (1), the mass ratio of the alcohol compound to L-LA and ε-CL is 1:(1-20):(3-8).

6. The method for preparing PLA-PCL polyester copolymer for biomass pressure-sensitive adhesive under non-catalytic conditions according to claim 1, characterized in that: The reaction processes of step (1) and step (2) are all carried out under an inert atmosphere.

7. The method for preparing PLA-PCL polyester copolymer for biomass pressure-sensitive adhesive under non-catalytic conditions according to claim 1, characterized in that: In step (2), the reaction temperature is 100°C to 240°C The reaction time is 9h to 15h.

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