CN104744878A - Polyformaldehyde compound POM-beta-CDPU with high thermal stability and preparation method thereof - Google Patents

Abstract

The invention discloses a polyoxymethylene compound POM-β-CDPU with high thermal stability and a preparation method thereof. The polyoxymethylene compound POM-β-CDPU blend includes polyoxymethylene and cyclodextrin inclusion compound, and the mass ratio of polyoxymethylene and cyclodextrin inclusion compound is 100:0.5-2. The specific method is to vacuum-dry polyoxymethylene and cyclodextrin inclusion compound at 80~110°C for 48~72 hours respectively; after drying, the mass ratio of polyoxymethylene and cyclodextrin inclusion compound is 100:0.5~2, add Put into the melting and mixing equipment, melt and knead at 180-200°C to obtain the mixture; discharge the mixture from the melting and mixing equipment, lower it to normal temperature and crystallize, and obtain the polyoxymethylene compound POM-β with high thermal stability - CDPU. The polyoxymethylene compound of the invention greatly improves the thermal stability of the polyoxymethylene and ensures the excellent mechanical properties of the material.

Description

A polyoxymethylene compound POM-β-CDPU with high thermal stability and preparation method thereof

technical field

The invention belongs to the technical field of polymer materials, and relates to a polyoxymethylene compound POM-β-CDPU with high thermal stability and a preparation method thereof, in particular to a cyclodextrin inclusion compound obtained by a cyclodextrin inclusion compound with high thermal stability Polyoxymethylene composite POM-β-CDPU with stability and excellent mechanical properties and a preparation method thereof.

Background technique

Polyoxymethylene (POM) is widely used because of its excellent comprehensive properties. Its main advantages include high strength, good rigidity, high hardness, excellent solvent resistance and corrosion resistance, and good molding performance, so it is very ideal. One of engineering plastics. However, due to its special molecular structure, its thermal stability is poor, and it will be degraded during melt processing, thereby producing a large amount of formaldehyde gas, which not only pollutes the environment, endangers human health, but is easily oxidized to formic acid, and leads to the occurrence of polyoxymethylene. Acid hydrolysis further reduces the material properties.

Contents of the invention

An object of the present invention is to provide a polyoxymethylene compound with high thermal stability against the deficiencies of the prior art.

The polyoxymethylene complex POM-β-CDPU with high thermal stability of the present invention is a blend, which includes polyoxymethylene (as a matrix) and cyclodextrin inclusion compound (as an additive); wherein polyoxymethylene and cyclodextrin The mass ratio of fine clathrate is 100:0.5~2;

As a preference, the mass ratio of polyoxymethylene to cyclodextrin inclusion compound is 100:2;

Another object of the present invention is to provide a method for preparing the above-mentioned polyoxymethylene complex POM-β-CDPU.

In order to solve the problems of the technologies described above, the technical means adopted in the present invention comprises the following steps:

Step (1). Vacuum-dry polyoxymethylene and cyclodextrin inclusion compound at 80-110°C for 48-72 hours;

Step (2). Add the dried polyoxymethylene and cyclodextrin clathrate in a mass ratio of 100:0.5-2, add it to the melting and mixing equipment, and perform melting and mixing at 180-200°C to obtain the mixture;

The melting and mixing equipment is internal mixer, single-screw extruder, twin-screw extruder;

For example, add the dried polyoxymethylene and cyclodextrin clathrate into the internal mixer for melting and mixing, the rotor speed of the internal mixer during premixing is 10-30rpm/min, melt and knead for 1-2min, and then increase the rotor speed Increase to 45~75rpm/min, melt and knead for 5~10min;

For example, adding the dried polyoxymethylene and cyclodextrin clathrate into a single-screw extruder or a twin-screw extruder for melting and mixing, the screw speed of the screw extruder is 10-20rpm/min when feeding, Increase the screw speed to 45~75rpm/min;

Step (3). The mixture is discharged from the melting and mixing equipment, lowered to normal temperature and crystallized to obtain a polyoxymethylene compound POM-β-CDPU with high thermal stability.

The cyclodextrin inclusion compound is formed by compounding cyclodextrin and polyurethane in DMF solvent (N,N-dimethylformamide), and the specific preparation is as follows: respectively prepare DMF solutions of cyclodextrin and polyurethane, and Add the DMF solution of polyurethane to the DMF solution of cyclodextrin dropwise at 50-90°C, heat and stir for 2-8 hours, then cool down to room temperature, and settle in excess distilled water after standing overnight to obtain the cyclodextrin inclusion compound of polyurethane , fully dried and ground for later use.

The mass ratio of polyurethane and cyclodextrin in cyclodextrin inclusion compound is 1: 10～20;

As preferably, the polyurethane is a polyester thermoplastic polyurethane elastomer;

Preferably, the cyclodextrin inclusion compound is an inclusion compound obtained by blending β-cyclodextrin and polyester thermoplastic polyurethane elastomer (TPU) in DMF solvent (N,N-dimethylformamide). thing;

As a preference, the polyoxymethylene and cyclodextrin clathrate after drying in step (2) are added to the melting and mixing equipment at a mass ratio of 100:2 for melting and mixing.

The beneficial effects of the present invention are:

The present invention innovatively uses a cyclodextrin inclusion compound as an additive to successfully modify POM, showing two advantages: (1) The composition is simple, and the addition amount is small, and the polymerization can be realized by simple addition. The thermal stability of formaldehyde materials has been greatly improved, which has never been reported before; (2) In addition, this kind of polyoxymethylene composites has improved strength while ensuring a certain elongation at break, which can meet actual needs.

The reason why the present invention chooses a cyclodextrin inclusion compound is as follows: (1) This cyclodextrin inclusion compound is a compound of polyurethane and cyclodextrin, and the amino group of TPU can effectively absorb the formaldehyde and formic acid released when POM degrades , and cyclodextrin can also adsorb the formaldehyde gas released during the decomposition of polyformaldehyde. In the cyclodextrin inclusion compound, the amino group and the hydroxyl group of the cyclodextrin work together to greatly improve the thermal stability of the material; (2) energy To a certain extent, the mechanical properties of the polyoxymethylene composite are guaranteed.

The polyoxymethylene compound of the invention greatly improves the thermal stability of polyoxymethylene, and ensures the excellent mechanical properties of the material, and can be applied in the fields of automobile industry, construction, electronic appliances and the like.

Description of drawings

Fig. 1 is the thermogravimetric analysis diagram of the material prepared by Comparative Example 1 and Example 2-1 under nitrogen atmosphere;

Fig. 2 is the derivative thermogravimetric analysis diagram of the material prepared by Comparative Example 1 and Example 2-1 under a nitrogen atmosphere;

Fig. 3 is a diagram of the mechanical properties of the materials prepared in Comparative Example 1 and Example 2-1.

Detailed ways

The present invention will be further analyzed below in conjunction with the accompanying drawings and specific embodiments.

First prepare cyclodextrin clathrate, specific examples are as follows:

Example 1-1.

Dissolve 10g of β-cyclodextrin in 30ml of DMF solvent and 1g of polyester thermoplastic polyurethane elastomer in 20mL of DMF solvent to obtain the DMF solution of cyclodextrin and the DMF solution of polyurethane respectively; then drop the above DMF solution of polyurethane at 70°C Add to the DMF solution of the above cyclodextrin, heat and stir for 4 hours, then cool down to room temperature, settle in excess distilled water after standing overnight to obtain the cyclodextrin inclusion complex of polyurethane, fully dry and grind for later use.

Example 1-2.

Dissolve 20g of β-cyclodextrin in 60ml of DMF solvent and 1g of polyester thermoplastic polyurethane elastomer in 20mL of DMF solvent to obtain the DMF solution of cyclodextrin and the DMF solution of polyurethane respectively; then drop the above DMF solution of polyurethane at 50°C Add it to the DMF solution of the above cyclodextrin, heat and stir for 8 hours, then cool down to room temperature, settle in excess distilled water after standing overnight to obtain the cyclodextrin inclusion complex of polyurethane, fully dry and grind it for later use.

Example 1-3.

Dissolve 15g of β-cyclodextrin in 45ml of DMF solvent and 1g of polyester thermoplastic polyurethane elastomer in 20mL of DMF solvent to obtain the DMF solution of cyclodextrin and the DMF solution of polyurethane respectively; then drop the above DMF solution of polyurethane at 90°C Add to the DMF solution of the above cyclodextrin, heat and stir for 2 hours, then cool down to room temperature, settle in excess distilled water after standing overnight to obtain the cyclodextrin inclusion compound of polyurethane, fully dry and grind for later use.

Then take the cyclodextrin inclusion compound prepared in Examples 1-1 to 1-3 to prepare a polyoxymethylene complex, and the specific examples are as follows:

Comparative example 1.

Step (1). Vacuum-dry polyoxymethylene at 80-110°C for 48-72 hours;

Step (2). Add 50g of dried polyoxymethylene into the internal mixer, melt and blend at 180~200°C, melt and knead at 10~30rpm/min for 1~2min, and then increase the rotor speed to 45~ 75rpm/min, melt and knead for 5-10min.

Step (3). The polyoxymethylene melt is discharged from the internal mixer, lowered to normal temperature and crystallized to obtain a polyoxymethylene material.

Example 2-1.

Step (1). Vacuum-dry polyoxymethylene and cyclodextrin inclusion complex at 80-110°C for 48-72 hours respectively;

Step (2). Add 50g of dried polyoxymethylene and 1g of dried cyclodextrin clathrate into the internal mixer, melt and blend at 180~200°C, melt and knead at 10~30rpm/min for 1 ~2min, then increase the rotor speed to 45~75rpm/min, melt and knead for 5~10min.

Step (3). The blend is discharged from the internal mixer, lowered to normal temperature and crystallized to obtain a polyoxymethylene composite material.

The mass ratio of polyoxymethylene to cyclodextrin inclusion compound in the polyoxymethylene compound prepared in Example 2-1 is 50:1.

The thermal stability test was carried out on the materials prepared in Comparative Example 1 and Example 2-1. The test conditions were as follows: from 30°C to 600°C at a heating rate of 10°C/min; nitrogen atmosphere.

Table 1 Comparative example 1, the thermal stability test result under nitrogen atmosphere of the material prepared by embodiment 2-1

sample T _5% (°C) T _50% (°C) T _max (°C) Comparative example 1 310.19 338.60 326.89 Example 2-1 344.5 397.8 400.00

As shown in Figures 1 and 2, see Table 1 for detailed data. The initial degradation temperature (T _5% ) of pure polyoxymethylene (Comparative Example 1) is only 310°C, and the corresponding temperature (T _50% ) at 50% degradation is about 340°C, the temperature (T _max ) corresponding to the maximum thermal weight loss is 327°C, indicating that the thermal stability of pure polyoxymethylene is very poor. After adding cyclodextrin inclusion compound, T _5% increased by 34.31°C, T _50% increased by 59.2°C, and T _max increased by 73.11°C, which proves that adding cyclodextrin inclusion compound can greatly improve the thermal stability of polyoxymethylene complex.

The mechanical properties of the materials prepared in Comparative Example 1 and Example 2-1 were tested, and the test conditions were: tensile rate 10 mm/min; normal temperature.

Table 2 Comparative Example 1, the basic mechanical properties of the material prepared by Example 2-1

sample Yield strength (MPa) Elongation at break (﹪) Comparative example 1 54.59 47.075 Example 2-1 53.90 24.694

As shown in Figure 3 and Table 2, after adding cyclodextrin inclusion compound in pure polyoxymethylene (Comparative Example 1), although the elongation at break decreased, the strength remained basically unchanged, which can meet the actual use requirements of the material.

Example 2-2.

Step (1). Vacuum-dry the polyoxymethylene and cyclodextrin inclusion complex at 80°C for 72 hours;

Step (2). Add the dried 50g polyoxymethylene and 0.25g cyclodextrin clathrate to the internal mixer and melt and knead at 180°C. During the premixing, the rotor speed of the internal mixer is 10rpm/min. Mix for 2 minutes, then increase the rotor speed to 45rpm/min, and melt and mix for 10 minutes;

Step (3). The mixture is discharged from the melting and mixing equipment, lowered to normal temperature and crystallized to obtain a polyoxymethylene compound POM-β-CDPU with high thermal stability.

Example 2-3.

Step (1). Vacuum-dry the polyoxymethylene and cyclodextrin inclusion compound at 110°C for 48 hours;

Step (2). Step (2). Add 50g of polyoxymethylene after drying and 1g of cyclodextrin inclusion compound to the internal mixer for melting and mixing at 180°C. The rotor speed of the internal mixer during premixing is 30rpm /min, melt and knead for 1min, then increase the rotor speed to 75rpm/min, and melt and knead for 5min;

Step (3). The mixture is discharged from the melting and mixing equipment, lowered to normal temperature and crystallized to obtain a polyoxymethylene compound POM-β-CDPU with high thermal stability.

Example 2-4.

Step (1). Vacuum-dry the polyoxymethylene and cyclodextrin inclusion complex at 90°C for 65 hours;

Step (2). Add polyoxymethylene after 50g drying, 0.5g cyclodextrin clathrate to single-screw extruder and carry out melt mixing under 190 ℃, the screw speed of screw extruder is 10rpm/ min, increase the screw speed to 45rpm/min during extrusion;

Step (3). The mixture is discharged from the melting and mixing equipment, lowered to normal temperature and crystallized to obtain a polyoxymethylene compound POM-β-CDPU with high thermal stability.

Example 2-5.

Step (1). Vacuum-dry the polyoxymethylene and cyclodextrin inclusion complex at 100°C for 55 hours;

Step (2). Add 50g of dried polyoxymethylene and 0.8g of cyclodextrin clathrate to a single-screw extruder for melting and mixing at 200°C. When feeding, the screw speed of the screw extruder is 20rpm/ min, increase the screw speed to 75rpm/min during extrusion;

Step (3). The mixture is discharged from the melting and mixing equipment, lowered to normal temperature and crystallized to obtain a polyoxymethylene compound POM-β-CDPU with high thermal stability.

Example 2-6.

Step (1). Vacuum-dry the polyoxymethylene and cyclodextrin inclusion complex at 105°C for 50 hours;

Step (2). Add 50g of dried polyoxymethylene and 0.6g of cyclodextrin clathrate to a twin-screw extruder for melting and mixing at 185°C. When feeding, the screw speed of the screw extruder is 10rpm/ min, increase the screw speed to 45rpm/min during extrusion;

Step (3). The mixture is discharged from the melting and mixing equipment, lowered to normal temperature and crystallized to obtain a polyoxymethylene compound POM-β-CDPU with high thermal stability.

Example 2-7.

Step (1). Vacuum-dry the polyoxymethylene and cyclodextrin inclusion complex at 90°C for 60 hours respectively;

Step (2). Add 50g of dried polyoxymethylene and 0.9g of cyclodextrin clathrate to a twin-screw extruder for melting and mixing at 200°C. When feeding, the screw speed of the screw extruder is 20rpm/ min, increase the screw speed to 75rpm/min during extrusion;

Step (3). The mixture is discharged from the melting and mixing equipment, lowered to normal temperature and crystallized to obtain a polyoxymethylene compound POM-β-CDPU with high thermal stability.

The above embodiments do not limit the present invention, and the present invention is not limited to the above embodiments, as long as the requirements of the present invention are met, they all belong to the protection scope of the present invention.

Claims (10)

1. one kind has the polyformaldehyde compound POM-β-CDPU of high thermal stability, and be blend, it is characterized in that this blend comprises polyoxymethylene, cyclodextrin inclusion compound, wherein the mass ratio of polyoxymethylene and cyclodextrin inclusion compound is 100:0.5 ~ 2;

Described cyclodextrin inclusion compound is that cyclodextrin and urethane are composited in DMF solvent.

2. a kind of polyformaldehyde compound POM-β-CDPU with high thermal stability as claimed in claim 1, is characterized in that the mass ratio of polyoxymethylene and cyclodextrin inclusion compound is 100:2.

3. a kind of polyformaldehyde compound POM-β-CDPU with high thermal stability as claimed in claim 1, it is characterized in that being prepared as follows of described cyclodextrin inclusion compound: the DMF solution preparing cyclodextrin, urethane respectively, at 50 ~ 90 DEG C, the DMF solution of urethane is dropped in the DMF solution of cyclodextrin, heated and stirred was down to normal temperature after 2 ~ 8 hours, after hold over night, in excessive distilled water, sedimentation obtains the cyclodextrin inclusion compound of urethane, for subsequent use after abundant drying and grinding;

In cyclodextrin inclusion compound, the mass ratio of urethane and cyclodextrin is 1:10 ~ 20.

4. a kind of polyformaldehyde compound POM-β-CDPU with high thermal stability as claimed in claim 3, is characterized in that described urethane is polyester type Polyurethane Thermoplastic Elastomer.

5. a kind of polyformaldehyde compound POM-β-CDPU with high thermal stability as claimed in claim 1, is characterized in that described cyclodextrin inclusion compound is beta-cyclodextrin and the polyester type Polyurethane Thermoplastic Elastomer inclusion compound that composite obtains in DMF solvent.

6. preparation a kind of method with the polyformaldehyde compound POM-β-CDPU of high thermal stability as claimed in claim 1, is characterized in that the method comprises the following steps:

Step (1). by polyoxymethylene and cyclodextrin inclusion compound vacuum-drying 48 ~ 72h at 80 ~ 110 DEG C respectively;

Described cyclodextrin inclusion compound is that cyclodextrin and urethane are composited in DMF solvent;

Step (2). be 100:0.5 ~ 2 in mass ratio by dried polyoxymethylene and cyclodextrin inclusion compound, join in melting mixing equipment, at 180 ~ 200 DEG C, carry out melting mixing, obtain mixture;

Step (3). by mixture discharging from melting mixing equipment, be down to normal temperature and crystallization, obtain the polyformaldehyde compound POM-β-CDPU of high thermal stability.

7. a kind of preparation method with the polyformaldehyde compound POM-β-CDPU of high thermal stability as claimed in claim 6, is characterized in that the melting mixing equipment described in step (2) is Banbury mixer, single screw extrusion machine, twin screw extruder;

Melting mixing is carried out as dried polyoxymethylene and cyclodextrin inclusion compound are added Banbury mixer, during premix, the spinner velocity of Banbury mixer is 10 ~ 30rpm/min, melting mixing 1 ~ 2min, is then promoted to 45 ~ 75rpm/min by spinner velocity, melting mixing 5 ~ 10min;

As dried polyoxymethylene and cyclodextrin inclusion compound added single screw extrusion machine or twin screw extruder carries out melting mixing, during feeding, the screw speed of screw extrusion press is 10 ~ 20rpm/min, when extruding, screw speed is promoted to 45 ~ 75rpm/min.

8. a kind of preparation method with the polyformaldehyde compound POM-β-CDPU of high thermal stability as claimed in claim 6, is characterized in that in step (2), dried polyoxymethylene, cyclodextrin inclusion compound carry out melting mixing for 100:2 joins melting mixing equipment in mass ratio.

9. a kind of preparation method with the polyformaldehyde compound POM-β-CDPU of high thermal stability as claimed in claim 6, it is characterized in that being prepared as follows of described cyclodextrin inclusion compound: the DMF solution preparing cyclodextrin, urethane respectively, at 50 ~ 90 DEG C, the DMF solution of urethane is dropped in the DMF solution of cyclodextrin, heated and stirred was down to normal temperature after 2 ~ 8 hours, after hold over night, in excessive distilled water, sedimentation obtains the cyclodextrin inclusion compound of urethane, for subsequent use after abundant drying and grinding;

In cyclodextrin inclusion compound, the mass ratio of urethane and cyclodextrin is 1:10 ~ 20;

As preferably, described urethane is polyester type Polyurethane Thermoplastic Elastomer.

10. a kind of preparation method with the polyformaldehyde compound POM-β-CDPU of high thermal stability as claimed in claim 6, is characterized in that described cyclodextrin inclusion compound is beta-cyclodextrin and the polyester type Polyurethane Thermoplastic Elastomer inclusion compound that composite obtains in DMF solvent.