阅读说明：本技术 一种软质pbat基生物可降解发泡材料的制备方法 (Preparation method of soft PBAT-based biodegradable foam material ) 是由 张须臻 周锦 南婧文 王秀华 施强 黄飞桥 于 2020-12-14 设计创作，主要内容包括：本发明公开了一种软质PBAT基生物可降解发泡材料的制备方法,其特征在于,包括如下步骤：1)通过硫酸酸解法制备纤维素纳米晶；2)纤维素纳米晶、聚对苯二甲酸己二酸丁二醇酯、扩链剂、发泡剂熔融共混得到熔体；3)将步骤2)中熔体减压降温挤出。本发明从原理上讲以多羟基CNC与PBAT酯基间作用引发物理交联点,将PBAT分子链交联在一起,使得分子间的作用力增加,分子的相对滑移减弱,使得本发明所制软质发泡材料比同类PBAT产品具有更好的抗蠕变性能；从工艺上大大简化了其他化学改性PBAT的工艺流程；从性能上,本发明所制软质泡沫材料与常规泡沫材料相比具有突出的生物可降解性能,环保优势明显。(The invention discloses a preparation method of a soft PBAT-based biodegradable foaming material, which is characterized by comprising the following steps: 1) preparing cellulose nanocrystalline by a sulfuric acid acidolysis method; 2) melting and blending cellulose nanocrystal, polybutylene terephthalate adipate, a chain extender and a foaming agent to obtain a melt; 3) and 3) decompressing, cooling and extruding the melt in the step 2). In principle, the invention uses the interaction between the polyhydroxy CNC and the PBAT ester group to initiate physical crosslinking points, and the PBAT molecular chains are crosslinked together, so that the intermolecular acting force is increased, the relative slippage of molecules is weakened, and the soft foaming material prepared by the invention has better creep resistance than similar PBAT products; the process flow of other chemical modification of PBAT is greatly simplified from the aspect of process; compared with the conventional foam material, the soft foam material prepared by the invention has outstanding biodegradable performance and obvious environmental protection advantage in performance.)

1. A preparation method of a soft PBAT-based biodegradable foaming material is characterized by comprising the following steps: 1) preparing cellulose nanocrystalline by a sulfuric acid acidolysis method; 2) melting and blending cellulose nanocrystal, polybutylene terephthalate adipate, a chain extender and a foaming agent to obtain a melt; 3) and 3) decompressing, cooling and extruding the melt in the step 2).

2. The method of claim 1, wherein the sulfuric acid hydrolysis method comprises dispersing cellulose microcrystals in a sulfuric acid solution, repeatedly washing the hydrolyzed suspension by a magnetic stirrer, centrifuging the washed suspension by a centrifuge until the pH value is neutral, adding 0.5% ammonia water dropwise into the suspension, washing with water, dialyzing the obtained cellulose nanocrystalline suspension in deionized water, and completely freeze-drying the solution after being placed in a refrigerator to obtain loose cellulose nanocrystalline powder;

the cellulose microcrystal raw material adopts one or more natural celluloses of cotton, cotton linter, rice hull, pine needle, hemp stalk and orange peel;

the concentration of the sulfuric acid solution is 60-70%;

the rotating speed of the magnetic stirrer is 100-120rpm, the reaction temperature is 55-65 ℃, and the reaction time is 6-7 h;

the rotating speed of the centrifuge is 10000-12000r/min, and the centrifugation time is 4-7 min;

the cellulose nanocrystalline suspension is dialyzed in deionized water for 12-24 h.

3. The method for preparing the soft PBAT-based biodegradable foam material according to claim 1, wherein the cellulose nanocrystals are melt-blended with polybutylene terephthalate adipate, a chain extender and a foaming agent, and the melt-blending comprises the following raw material components in parts by weight: 1-100 parts of polybutylene terephthalate adipate, 1-20 parts of cellulose nanocrystals, 1-10 parts of chain extender and 0.1-15 parts of foaming agent;

the chain extender is one of a long-chain polyurethane prepolymer capped by diisocyanate or a long-chain polymer capped by epoxy groups at two ends;

the foaming agent is one of a physical foaming agent or a chemical foaming agent, wherein the physical foaming agent adopts supercritical CO₂Supercritical N₂And supercritical butane; the chemical foaming agent is one of azo compounds, sulfonyl hydrazine compounds, calcium carbonate and sodium bicarbonate.

4. The method of claim 3, wherein the chain extender is one of toluene-2, 4 diisocyanate and diphenylmethane diisocyanate; the chemical foaming agent of the azo compound is azodicarbonamide, and the chemical foaming agent of the sulfonyl hydrazide compound is 4, 4-oxo-bis-benzenesulfonyl hydrazide.

5. The method for preparing the soft PBAT-based biodegradable foam material according to claim 1, wherein the blending step in the step 2) is specifically as follows:

(1) placing polybutylene terephthalate adipate in a vacuum oven to be dried for 12 hours at the temperature of 80 ℃;

(2) taking polybutylene terephthalate adipate, cellulose nanocrystals, a chain extender and a foaming agent, fully mixing and melting by adopting respective multipoint adding modes under the rotation of a double screw to obtain a homogeneous system.

6. The method for preparing the soft PBAT-based biodegradable foam material according to claim 1, wherein the step of extruding the melt in the step 3) by reducing the pressure and the temperature specifically comprises the following steps: and (3) depressurizing and cooling the melt obtained in the step 2) in an extrusion die head to nucleate and grow foam pores, and finally cooling and shaping to obtain the soft polybutylene terephthalate adipate foaming material.

Technical Field

The invention relates to the field of foaming materials, in particular to a preparation method of a soft PBAT-based biodegradable foaming material.

Background

With the rapid development of electronic information technology, the online shopping industry and the take-out industry rise rapidly and occupy more and more important positions in our lives, and the express logistics generated by the online shopping industry and the take-out industry become an important part of the electronic information technology. In order to avoid damage to the product during transportation, anti-collision foam has become an essential material in express delivery. Currently, most of the widely used foaming materials are made of Polyethylene (PE), Polystyrene (PS), Polyurethane (PU), and the like. Among them, the PS foamed product is a material with a large using amount at present, but the PS foamed product is difficult to degrade and seriously damages the environment, so the PS foamed product is called white pollution, and the PU foamed sheet can generate isocyanate residues harmful to human bodies in the foaming process and cannot be recycled after being used. The large amount of the foaming materials used and the non-degradability bring great pressure to the environment, so the preparation of the biodegradable foaming materials becomes a problem to be solved urgently in the whole society at present.

At present, the biodegradable materials with the highest industrialization degree are polylactic acid and polybutylene terephthalate adipate (PBAT), wherein the PBAT has larger future development potential because monomers can be extracted from petroleum derivatives. PBAT has been widely used as a packaging material for garbage bags, food packaging bags, film packaging and the like, and has applications in the fields of sanitary goods such as cotton swabs and the like, and biomedicine (property and application of PBAT composite material [ J ] Anhui chemical engineering, 2020,225(03): 14-18.). But the foam material field which is used in a large amount in express logistics at present is not applied, and the main reason is that the PBAT has the performance defects of strong creep property, low melt strength and the like. In the preparation of polymeric foams, cells are generally introduced into a polymeric matrix, the conventional method being the addition of a blowing agent. During the formation of a large number of bubbles, the polymer melt exists as a spacer film between the bubbles, and the more bubbles per unit volume, the thinner the thickness of the spacer film of the melt. Thus, the production of commercial foams requires that the polymer melt have a relatively high melt strength to support the formation of very thin cell membranes. In patent CN108264736B, a PBAT extrusion foaming preparation method is introduced, which optimizes the operation time and temperature window of foaming, but the PBAT foaming material has low creep resistance, is easy to generate plastic permanent deformation during use, and has low practicability.

The creep performance of the high polymer generally originates from the slippage among molecular chains, and chemical or physical cross-linking points can be introduced among the molecular chains of the high polymer to inhibit the slippage among the molecular chains, thereby effectively controlling the creep behavior of the high polymer. For PBAT, due to the chemical sensitivity of aliphatic polyester, the molecular chain of PBAT is easily cracked by chemical modification, so that the PBAT performance is reduced. Therefore, the introduction of crosslinking points by physical methods in PBAT systems is a preferred solution. Liuwei and the like add active calcium silicate powder into a PBAT material to form a temporary physical crosslinking structure between PBAT molecules, reduce the movement capacity of a molecular chain, and the calcium carbonate powder can promote heterogeneous nucleation of cells during PBAT foaming so as to improve the expandability of the PBAT and prepare the PBAT foaming material (Liuwei, Ninggan, and the like, the influence of calcium silicate on the rheological property and the foaming behavior of the PBAT [ J ] engineering plastic application, 2017(3): 116-. However, due to the significant flexibility of the PBAT molecular chain, the extent of crystallinity enhancement of PBAT is still very limited despite the introduction of nucleating agents. Therefore, other alternatives are sought, and the introduction of a controllable amount of physical crosslinking points with strong binding force into the PBAT system becomes urgent priority for creep resistance modification of PBAT foam materials.

Disclosure of Invention

The invention provides a preparation method of a soft PBAT-based biodegradable foaming material aiming at the defects of low strength and easy creep of PBAT melt in the prior art, wherein CNC is used as a physical cross-linking agent, and because a large amount of hydroxyl groups are arranged on the surface of the CNC, the CNC can simultaneously form hydrogen bonds with ester bonds in adjacent PBAT molecules to play a role in bridging and increase the acting force among the PBAT molecules, so that the creep resistance of the foaming material is improved, the resilience capability of the material is enhanced, the service life is prolonged, and the preparation method has wider application.

In order to achieve the purpose, the technical scheme of the invention is as follows:

a preparation method of a soft PBAT-based biodegradable foaming material comprises the following steps: 1) preparing Cellulose Nanocrystals (CNC) by a sulfuric acid acidolysis method; 2) melting and blending Cellulose Nanocrystal (CNC), polybutylene terephthalate adipate (PBAT), a chain extender and a foaming agent to obtain a melt; 3) and 3) decompressing, cooling and extruding the melt in the step 2).

The sulfuric acid acidolysis method comprises the steps of dispersing cellulose microcrystals into a sulfuric acid solution, repeatedly washing a hydrolyzed suspension by using a magnetic stirrer, centrifuging the hydrolyzed suspension to a neutral pH value by using a centrifugal machine, dripping 0.5% ammonia water into the suspension, washing the suspension by using water, dialyzing the obtained Cellulose Nanocrystalline (CNC) suspension in deionized water, and completely freezing and drying the obtained solution after the solution is placed in a refrigerator to obtain loose Cellulose Nanocrystalline (CNC) powder;

the cellulose microcrystal raw material adopts one or more natural celluloses of cotton, cotton linter, rice hull, pine needle, hemp stalk and orange peel;

the concentration of the sulfuric acid solution is 60-70%;

the rotating speed of the magnetic stirrer is 100-120rpm, the reaction temperature is 55-65 ℃, and the reaction time is 6-7 h;

the rotating speed of the centrifuge is 10000-12000r/min, and the centrifugation time is 4-7 min;

the Cellulose Nanocrystal (CNC) suspension is dialyzed in deionized water for 12-24 h.

The Cellulose Nanocrystalline (CNC) is melt-blended with polybutylene terephthalate adipate (PBAT), a chain extender and a foaming agent, wherein the melt-blended raw materials comprise the following components in parts by weight: 1-100 parts of polybutylene terephthalate adipate, 1-20 parts of cellulose nanocrystals, 1-10 parts of chain extender and 0.1-15 parts of foaming agent;

the chain extender is one of a long-chain polyurethane prepolymer capped by diisocyanate or a long-chain polymer capped by epoxy groups at two ends;

the foaming agent is one of a physical foaming agent or a chemical foaming agent, wherein the physical foaming agent adopts supercritical CO₂Supercritical N₂And supercritical butane; the chemical foaming agent is one of azo compounds, sulfonyl hydrazine compounds, calcium carbonate and sodium bicarbonate.

The chain extender is preferably one of toluene-2, 4 diisocyanate (TDI) and diphenylmethane diisocyanate (MDI); the chemical foaming agent of the azo compound is preferably Azodicarbonamide (AC); the chemical foaming agent of the sulfonyl hydrazide compound is preferably 4, 4-oxo-bis-benzenesulfonyl hydrazide (OBSH).

The blending step in the step 2) is specifically as follows:

(1) placing polybutylene terephthalate adipate (PBAT) in a vacuum oven to dry for 12 hours at 80 ℃;

(2) taking polybutylene terephthalate adipate (PBAT), Cellulose Nanocrystalline (CNC), a chain extender and a foaming agent, and fully mixing and melting the components in a multi-point adding mode under the rotation of a double screw to obtain a homogeneous system.

The step 3) of decompressing, cooling and extruding the melt specifically comprises the following steps: and (3) depressurizing and cooling the melt obtained in the step 2) in an extrusion die head to nucleate and grow foam pores, and finally cooling and shaping to obtain the soft polybutylene terephthalate adipate (PBAT) foaming material.

The invention has the beneficial effects that: in principle, the invention uses the interaction between the polyhydroxy CNC and the PBAT ester group to initiate physical crosslinking points, and the PBAT molecular chains are crosslinked together, so that the intermolecular acting force is increased, the relative slippage of molecules is weakened, and the soft foaming material prepared by the invention has better creep resistance than similar PBAT products; in terms of process, the PBAT can be prepared by a one-step method only by simply melting and blending the PBAT, the CNC, the chain extender and the foaming agent, so that the process flow of other chemically modified PBAT is greatly simplified; compared with the conventional foam material, the soft foam material prepared by the invention has outstanding biodegradable performance and obvious environmental protection advantage in performance.

Detailed Description

Example 1

The preparation method of the soft PBAT-based biodegradable foam material of the embodiment comprises the following steps:

1) 20.0g of the cellulose microcrystals are dispersed in 150ml of a 60% (v/v) strength sulfuric acid solution and the hydrolysis is completed by reaction for 6 hours at 55 ℃ with magnetic stirring at a rate of 100 rpm. The hydrolyzed suspension was repeatedly washed with deionized water and centrifuged at 10000r/min at high speed for 4min until the pH was neutral. Ammonia water (0.5%) is dripped into the suspension to adjust the pH value to 7, the suspension is washed by water again, the obtained CNC suspension is dialyzed in deionized water for 12 hours, and after the suspension is placed in a refrigerator to be iced, the suspension is completely frozen and dried to obtain loose CNC powder;

2) PBAT is dried in a vacuum oven at 80 ℃ for 12 hours, 100 parts of PBAT and 20 parts of CNC are taken, 5 parts of chain extender (toluene-2, 4 diisocyanate TDI is adopted in the embodiment) and 15 parts of foaming agent (supercritical CO is adopted in the embodiment)₂) Adding the raw materials at multiple points, fully mixing and melting under the rotation of a double screw, and controlling the temperature to be 150 ℃;

3) and (3) depressurizing and cooling the homogeneous system obtained by melting and diffusing in the step (2) in an extrusion die head to nucleate and grow foam pores, and finally cooling and shaping to obtain the soft PBAT foaming material.

In principle, the embodiment uses the interaction between the polyhydroxy CNC and the PBAT ester group to initiate physical crosslinking points, and the PBAT molecular chains are crosslinked together, so that the intermolecular acting force is increased, the relative slippage of molecules is weakened, and the soft foaming material prepared by the embodiment has better creep resistance than similar PBAT products; in terms of process, the PBAT can be prepared by a one-step method only by simply melting and blending the PBAT, the CNC, the chain extender and the foaming agent, so that the process flow of other chemically modified PBAT is greatly simplified; from the aspect of performance, compared with the conventional foam material, the soft foam material prepared by the embodiment has outstanding biodegradable performance and obvious environmental protection advantage.

Example 2

The preparation method of the soft PBAT-based biodegradable foam material of the embodiment comprises the following steps:

1) 20.0g of the cellulose microcrystals are dispersed in 150ml of 70% (v/v) sulfuric acid solution and reacted by magnetic stirring at 120rpm for 7 hours at 65 ℃. The hydrolyzed suspension was repeatedly washed with deionized water and centrifuged at high speed at 12000r/min for 7min until the pH was neutral. Ammonia water (0.5%) is dripped into the suspension to adjust the pH value to 7, the suspension is washed by water again, the obtained CNC suspension is dialyzed in deionized water for 24 hours, and after the suspension is placed in a refrigerator to be iced, the suspension is completely frozen and dried to obtain loose CNC powder;

2) drying PBAT in a vacuum oven at 80 ℃ for 12 hours, adding 2 parts of chain extender (toluene-2, 4-diisocyanate TDI is adopted in the embodiment) and 4 parts of foaming agent (supercritical butane is adopted in the embodiment) into 90 parts of PBAT and 10 parts of CNC, adding the chain extender and the foaming agent at multiple points, fully mixing and melting under the rotation of a double screw, and controlling the temperature to be 150 ℃;

3) and (3) depressurizing and cooling the homogeneous system obtained by melting and diffusing in the step (2) in an extrusion die head to nucleate and grow foam pores, and finally cooling and shaping to obtain the PBAT foaming material.

In principle, the embodiment uses the interaction between the polyhydroxy CNC and the PBAT ester group to initiate physical crosslinking points, and the PBAT molecular chains are crosslinked together, so that the intermolecular acting force is increased, the relative slippage of molecules is weakened, and the soft foaming material prepared by the embodiment has better creep resistance than similar PBAT products; in terms of process, the PBAT can be prepared by a one-step method only by simply melting and blending the PBAT, the CNC, the chain extender and the foaming agent, so that the process flow of other chemically modified PBAT is greatly simplified; from the aspect of performance, compared with the conventional foam material, the soft foam material prepared by the embodiment has outstanding biodegradable performance and obvious environmental protection advantage.

Example 3

The preparation method of the soft PBAT-based biodegradable foam material of the embodiment comprises the following steps:

1) 20.0g of the cellulose microcrystals were dispersed in 150ml of a 65% (v/v) sulfuric acid solution and reacted at 60 ℃ for 6.5 hours by magnetic stirring at a rate of 110rpm to complete the hydrolysis. The hydrolyzed suspension was repeatedly washed with deionized water and centrifuged at high speed at 11000r/min for 5min until the pH was neutral. Ammonia water (0.5%) is dripped into the suspension to adjust the pH value to 7, the suspension is washed by water again, the obtained CNC suspension is dialyzed in deionized water for 18 hours, and after the suspension is placed in a refrigerator to be iced, the CNC suspension is completely frozen and dried to obtain loose CNC powder;

2) drying PBAT in a vacuum oven at 80 ℃ for 12 hours, adding 5 parts of chain extender (diphenylmethane diisocyanate MDI is adopted in the embodiment) and 10 parts of foaming agent (azodicarbonamide AC is adopted in the embodiment) into 80 parts of PBAT and 15 parts of CNC, adding the chain extender and the foaming agent at multiple points, fully mixing and melting under the rotation of twin screws, and controlling the temperature to be 150 ℃;

3) and (3) depressurizing and cooling the homogeneous system obtained by melting and diffusing in the step (2) in an extrusion die head to nucleate and grow foam pores, and finally cooling and shaping to obtain the soft PBAT foaming material.

In principle, the embodiment uses the interaction between the polyhydroxy CNC and the PBAT ester group to initiate physical crosslinking points, and the PBAT molecular chains are crosslinked together, so that the intermolecular acting force is increased, the relative slippage of molecules is weakened, and the soft foaming material prepared by the embodiment has better creep resistance than similar PBAT products; in terms of process, the PBAT can be prepared by a one-step method only by simply melting and blending the PBAT, the CNC, the chain extender and the foaming agent, so that the process flow of other chemically modified PBAT is greatly simplified; from the aspect of performance, compared with the conventional foam material, the soft foam material prepared by the embodiment has outstanding biodegradable performance and obvious environmental protection advantage.

Example 4

The preparation method of the soft PBAT-based biodegradable foam material of the embodiment comprises the following steps: compared with the example 1, except that the foaming agent in the example adopts 4, 4-oxo-bis-benzenesulfonyl hydrazide OBSH, and the formula of each raw material component is changed as follows: the parameters are the same as in example 1 except that 50 parts of PBAT, 10 parts of CNC, 3 parts of chain extender and 5 parts of foaming agent are used.

In principle, the embodiment uses the interaction between the polyhydroxy CNC and the PBAT ester group to initiate physical crosslinking points, and the PBAT molecular chains are crosslinked together, so that the intermolecular acting force is increased, the relative slippage of molecules is weakened, and the soft foaming material prepared by the embodiment has better creep resistance than similar PBAT products; in terms of process, the PBAT can be prepared by a one-step method only by simply melting and blending the PBAT, the CNC, the chain extender and the foaming agent, so that the process flow of other chemically modified PBAT is greatly simplified; from the aspect of performance, compared with the conventional foam material, the soft foam material prepared by the embodiment has outstanding biodegradable performance and obvious environmental protection advantage.

Example 5

The preparation method of the soft PBAT-based biodegradable foam material of the embodiment comprises the following steps: compared with the example 1, except that the foaming agent in the example adopts calcium carbonate, and the formula of each raw material component is changed into: PBAT of 20 parts, CNC of 5 parts, chain extender of 2 parts and foaming agent of 3 parts, and the other parameters are the same as those in example 1.

In principle, the embodiment uses the interaction between the polyhydroxy CNC and the PBAT ester group to initiate physical crosslinking points, and the PBAT molecular chains are crosslinked together, so that the intermolecular acting force is increased, the relative slippage of molecules is weakened, and the soft foaming material prepared by the embodiment has better creep resistance than similar PBAT products; in terms of process, the PBAT can be prepared by a one-step method only by simply melting and blending the PBAT, the CNC, the chain extender and the foaming agent, so that the process flow of other chemically modified PBAT is greatly simplified; from the aspect of performance, compared with the conventional foam material, the soft foam material prepared by the embodiment has outstanding biodegradable performance and obvious environmental protection advantage.

Example 6

The preparation method of the soft PBAT-based biodegradable foam material of the embodiment comprises the following steps: compared with the embodiment 1, except that the foaming agent in the embodiment adopts sodium bicarbonate, and the formula of each raw material component is changed as follows: PBAT is 1 part, CNC is 1 part, chain extender is 1 part, foaming agent is 0.1 part, and other parameters are the same as example 1.

In principle, the embodiment uses the interaction between the polyhydroxy CNC and the PBAT ester group to initiate physical crosslinking points, and the PBAT molecular chains are crosslinked together, so that the intermolecular acting force is increased, the relative slippage of molecules is weakened, and the soft foaming material prepared by the embodiment has better creep resistance than similar PBAT products; in terms of process, the PBAT can be prepared by a one-step method only by simply melting and blending the PBAT, the CNC, the chain extender and the foaming agent, so that the process flow of other chemically modified PBAT is greatly simplified; from the aspect of performance, compared with the conventional foam material, the soft foam material prepared by the embodiment has outstanding biodegradable performance and obvious environmental protection advantage.