CN112375352A

CN112375352A - Low-temperature thermoplastic material and preparation method thereof

Info

Publication number: CN112375352A
Application number: CN202011086095.5A
Authority: CN
Inventors: 吴嘉梁; 刘海宏; 章中群; 林才生
Original assignee: Klarity Medical & Equipment Gz Co ltd
Current assignee: Klarity Medical & Equipment Gz Co ltd
Priority date: 2020-10-12
Filing date: 2020-10-12
Publication date: 2021-02-19
Anticipated expiration: 2040-10-12
Also published as: CN112375352B

Abstract

A polycaprolactone low-temperature thermoplastic material and a preparation method thereof. Compared with the existing polycaprolactone type low-temperature thermoplastic product, the formed low-temperature thermoplastic material has the advantages of smaller shrinkage force, better comfort, more uniform stretching and better fixing strength, and is more suitable for hospitals or other radiotherapy units and matched with three-dimensional conformal radiotherapy instruments for tumor surgery.

Description

Low-temperature thermoplastic material and preparation method thereof

Technical Field

The invention relates to a low-temperature thermoplastic material, in particular to a low-temperature thermoplastic radiation therapy fixing material and a preparation process thereof.

Background

The low-temperature thermoplastic material is prepared by taking polycaprolactone as a main component and adding additives, and is characterized in that: it can be softened and molded into any shape when heated to a certain temperature (about 65 ℃), and has the rigidity of plastic when cooled to normal temperature. The characteristics can be used for accurate positioning of tumor patients during radiotherapy. The low-temperature thermoplastic material is widely used for preparing radiotherapy positioning film products at present.

Although the existing polycaprolactone type low-temperature thermoplastic radiotherapy positioning product is convenient to form, the shrinkage force is large in the forming process, and strong compression force can be generated on a patient, so that severe discomfort can be caused. Moreover, because the rigidity of the raw materials is insufficient, the deformation resistance after shaping is poor, and the shaking of the key parts of the patient in the treatment process can seriously affect the precision and the radiotherapy quality of the later-stage tumor radiotherapy.

In order to solve the problem of how to improve the comfort of patients and the precision of radiotherapy in the radiotherapy process, at present, a polycaprolactone + carbon fiber composition (Chinese patent, grant publication No. CN101062977B) which can reduce the contraction force and has better fixing strength is provided, but carbon fibers can influence the imaging effect of nuclear magnetic resonance equipment, and because the resolution of nuclear magnetic resonance on soft tissues is superior to that of other equipment, nuclear magnetic resonance imaging technology is adopted in more and more radiotherapy departments, so that the carbon fiber low-temperature thermoplastic material is limited in clinical application.

Foreign countries also have reinforced low temperature thermoplastic materials made of kevlar + polycaprolactone, which, although well fixed, is very expensive.

Disclosure of Invention

The novel low-temperature thermoplastic material for radiotherapy positioning is prepared by combining the special requirements of the low-temperature thermoplastic material for radiotherapy, has higher rigidity and fixing effect than common low-temperature thermoplastic materials, and has the advantages of lower shrinkage force, easiness in stretching and shaping, lower cost and the like.

In order to achieve the above object, a first aspect of the present invention provides a low-temperature thermoplastic material comprising polycaprolactone and glass fibers, having a gel content of 20% or more (i.e., the material has a certain crosslinked network structure, and the gel content measured in a good solvent is 20% or more); wherein the mass ratio of the polycaprolactone to the glass fiber is 65:35-95:5 (namely, the glass fiber accounts for 5% -35% of the total mass of the polycaprolactone and the glass fiber).

The gel content refers to gel content data obtained by measuring the whole product. Specifically, according to the requirements of product cost and efficiency, the product with the gel content of 20-100% is obtained through the parameter control of the crosslinking process (the type and the amount of the crosslinking agent; and the parameters of the crosslinking process such as irradiation dose and time). In some embodiments, the gel content may be 20%, 30%, 40%, 50%, 70%, or 100%.

The method for measuring the gel content comprises the following steps: weighing a sample with the mass m1, adding the sample into a solvent, placing the sample in a proper environment, extracting the sample after swelling, drying the sample until the mass is constant, and weighing the mass m 2. The gel content is Vc m2/m1 × 100%.

In some embodiments, the specific method of determining gel content is: weighing a sample with the mass m1, putting the sample into a ground bottle filled with 25mL of toluene, tightly covering the bottle cap, putting the bottle in a constant-temperature oven at 25 ℃ to swell for 48 hours, and taking out the sample. The sample was then extracted for 24 hours and finally the sample was dried in a vacuum oven at 50 ℃ until the mass was constant and the mass was weighed to give a mass m 2. The gel content is Vc m2/m1 × 100%.

The polycaprolactone of the low-temperature thermoplastic material is a composite material of a matrix, and the required low-temperature thermoplastic material can be obtained by generally subjecting raw materials (polycaprolactone and glass fiber) to forming and crosslinking processes. Accordingly, a second aspect of the present invention is to provide a process for producing the above low temperature thermoplastic material obtained by subjecting polycaprolactone and glass fiber to a molding and crosslinking process.

Specifically, the method for manufacturing the low-temperature thermoplastic material comprises the following steps:

(1) mixing polycaprolactone, glass fiber and a cross-linking agent to obtain a composition; wherein the mass ratio of the polycaprolactone to the glass fiber is 65:35-95: 5;

(2) carrying out a molding process on the uniformly mixed composition to obtain a blank;

(3) and (3) carrying out a cross-linking process on the blank to obtain the low-temperature thermoplastic material with the gel content of more than or equal to 20%.

Specifically, the molding process in the above method refers to a process of forming plastic raw materials in various forms (powder, granule, solution and dispersion) into a product or blank in a desired shape by a specific method. Generally, the process comprises heating the raw materials to a fluid state (e.g., molten state), then obtaining a shape by, for example, placing in a mold, and finally cooling and setting.

It will be understood that the present invention is not intended to be limited to the shape of the blank and the final product. In some embodiments, the blank and ultimately the cryogenic thermoplastic material is a sheet material in order to produce a radiation therapy positioning product suitable for a specific location. In other embodiments, the material can be a film, a tube, a plate, a bar, a strip, or other special-shaped material with a complex cross section; for example, in other embodiments where the product is used for finger positioning, the blank, and ultimately the low temperature thermoplastic material, may be a tube.

To obtain blanks of different shapes, the present invention may employ various suitable forming methods including, but not limited to, injection, extrusion, calendering, blow molding, and the like. For example, in some embodiments, to obtain a sheet for a radiotherapeutic positioning product, the above composition may be heated to a molten state (generally, a heating temperature of 65 ℃ to 160 ℃), and then sheet-shaped by, for example, an extrusion or injection process. In addition, as a process well known to those skilled in the art, in order to obtain effects such as ventilation and heat dissipation during use (radiotherapy), the sheet (blank) may be perforated (punched) as required before or after crosslinking. For example, a punching machine can be used to punch holes in a specific mesh ratio before the crosslinking process; this proportion may be between 1% and 50% according to the specific application and requirements.

It is to be noted that the present invention is characterized by limiting the filler to the glass fiber, and its specific amount and/or (to be mentioned later) aspect ratio, rather than the forming process of the material. The invention has universality to the common molding process; compared with the prior art, the invention can obtain the beneficial effects stated in the specification under the condition of adopting the same process indexes.

Specifically, the crosslinking process in the above method refers to a process of forming a network or a body-type polymer by covalent bonds among the chains of the polymer (polycaprolactone) in the raw material, and includes chemical crosslinking and physical crosslinking. Physical crosslinking is the crosslinking of polymers by irradiation with light, heat, or the like. For the purposes of the present invention, the usual crosslinking methods for polycaprolactone can be employed. In some embodiments, the present invention employs irradiation crosslinking, the irradiation source may be a high energy electron accelerator, a cobalt source, X-rays or ultraviolet light, and the irradiation dose is 2-30KGy, preferably 2-10KGy, more specifically 4-7 KGy; for example, in some embodiments the dose is 4KGy, and in other embodiments the dose is 7 KGy.

The cross-linking agent allows the polycaprolactone to cross-link under the appropriate conditions and to obtain a low-temperature thermoplastic material. Generally, the amount of the conventional cross-linking agent is 0.05-5% of the total mass of polycaprolactone and glass fiber according to the requirements of the target product. In some embodiments, the crosslinker is triallyl isocyanurate.

It is to be noted here that the present invention of the present invention is characterized by limiting the filler to the glass fibers, and to the specific amount and/or (mentioned later) aspect ratio thereof, rather than to the crosslinking process of the material. The invention has universality to the common crosslinking process suitable for polycaprolactone; compared with the prior art, the invention can obtain the beneficial effects stated in the specification by adopting the same process index as long as the cross-linking process can obtain the target gel content.

According to the requirements of product cost and efficiency, the product with 20-100% of gel content is obtained through the parameter control of the crosslinking process (the type and the dosage of the crosslinking agent; and the parameters of the crosslinking process such as irradiation dose and time). In some embodiments, the gel content may be 20%, 30%, 40%, 50%, 70%, or 100%. For example, in some embodiments, the crosslinking agent triallyl isocyanurate is used for radiation crosslinking at a suitable dose, and the radiation dose is selected to be 7KGy, and the required gel content can be obtained by controlling the radiation time. For example, in some embodiments, the gel content obtained is 40%; while in other embodiments, the gel content obtained is 20%, 30%, 50%, 70%, or 100%.

It will be understood that the process for the preparation of the low-temperature thermoplastic material according to the invention is not limited solely to the above-listed processes. The polycaprolactone-based composite material with corresponding component content and gel content can also be obtained by other methods in the prior art.

The low-temperature thermoplastic material can be applied to the fixation/positioning of human body parts or joints, particularly when a nuclear magnetic resonance imaging technology is adopted; because the imaging effect of nuclear magnetic resonance equipment can be influenced by common materials such as carbon fiber and the like, the polycaprolactone/glass fiber composite low-temperature thermoplastic material is more suitable for a positioning technology adopting a nuclear magnetic resonance imaging technology.

A third aspect of the present invention therefore consists in providing the use of the above-mentioned cryogenic thermoplastic material for the preparation of a device for immobilizing a human region or joint, in particular for preparing a device suitable for use in magnetic resonance imaging techniques. The device for immobilizing the human body part or the joint is obtained by making a low-temperature thermoplastic material into a specific shape suitable for preservation, transport or application. The specific shape suitable for storage, transportation or application may be obtained by customizing a mold in a molding process, or by a method such as cutting before a crosslinking process after the molding process, or by a method such as cutting after the crosslinking process.

In particular, in some embodiments, the material can be used to prepare fixation devices for radiation therapy, such as head and neck and shoulder positioning films, body positioning plates, and the like. Of course, the cryogenic thermoplastic material is not limited to the preparation of positioning devices for radiation therapy. In view of its low temperature thermoplastic properties, and suitable stiffness and shrinkage force parameters, it is also applicable to other aspects including, but not limited to: fixation after surgical treatment of soft tissue injury such as joint ligament and nerve tendon injury; fixation after fracture and joint dislocation reduction; fixation after burns and other orthopedic surgery. For example, the method can be used for preparing fracture fixation splints. Since these aspects may also relate to the use of magnetic resonance imaging techniques, the use of the present invention would be advantageous and less restrictive than other prior art polycaprolactone low temperature thermoplastic materials.

In a fourth aspect of the invention, a device for immobilizing a human ground or joint is provided, the body of which is made of the above-mentioned cryogenic thermoplastic material. It will be readily appreciated that, in addition to the body made of the aforementioned low-temperature thermoplastic material, the device may also comprise other auxiliary parts, such as straps, etc. for auxiliary fixing.

The use method of the device mainly comprises the following steps:

(1) placing the device in an environment at the softening temperature of the low-temperature thermoplastic material so that the device softens;

(2) placing the softened device on a part or joint to be fixed for shaping;

(3) and cooling and shaping the device.

Specifically, the above softening temperature is 60 to 70 ℃ depending on the composition of the material. Thus, step (1) may be carried out by placing the device in water at 60-70 ℃ so that the device softens.

Specifically, the cooling setting of the material (device) is generally performed below the softening temperature. In order to make the human body comfortable, step (3) is preferably performed at normal or room temperature. In some embodiments, step (3) is performed at 15 ℃ to 30 ℃.

The comprehensive performance of the low-temperature thermoplastic material can meet the application requirement and is superior to other materials, particularly the bending strength; under the same addition amount (5% -35%), the glass fiber reinforced material is superior to other reinforced filling materials suitable for the nuclear magnetic resonance imaging technology, and has stronger deformation resistance. When being applied to human body part fixedly, for example radiotherapy location, because radiotherapy location diaphragm effect is fixed patient's head or parts such as neck chest, prevent that radiotherapy in-process patient from removing, the resistant deformability of diaphragm material is better, then the fixity after moulding on patient's health is better. That is, the fixing accuracy of the diaphragm made of the low-temperature thermoplastic material of the present invention is higher than that of the diaphragm made of other reinforced filling materials, especially other reinforced filling materials suitable for the magnetic resonance imaging technology.

In addition to flexural strength, the low temperature thermoplastic material of the present invention also has a lower cold set compression force than other materials. In the application of human body part/joint fixation, the material is used for preparing a fixing device, the part/joint fixation is realized through the process of firstly heating for softening and then cooling and shaping at normal temperature, and the lower the cooling compression force is, the higher the comfort of a user in clinic is.

Finally, the beneficial effects of the invention are as follows: experiments prove that compared with the existing polycaprolactone type low-temperature thermoplastic product, the low-temperature thermoplastic material prepared by the invention has the advantages of smaller formed shrinkage force, better comfort, more uniform stretching and better fixing strength, thereby being more suitable for hospitals or other radiotherapy units and being matched with three-dimensional conformal radiotherapy instruments for use in tumor operations.

Notwithstanding the above-mentioned advantages and others, the materials and devices of the present invention have this certain limitation in certain specific applications. For example, in applications involving stretching, particularly stretching to a certain extent or more (e.g., stretch-forming a softened material in certain locations), a certain proportion of the product may break and be unusable. The inventors have found through experiments that long glass fibers or chopped glass fibers commonly used in the art may be one of the factors causing the above-mentioned limitations.

Therefore, in order to increase the application range of the low-temperature thermoplastic material and the fixing device, especially the application process which needs to be stretched, more especially the application process which needs to be stretched to a certain extent or more, as a further preferable scheme of the invention, the mass ratio of the polycaprolactone to the glass fiber is 75:25-85:15 (namely, the glass fiber accounts for 15% -25% of the total mass of the polycaprolactone and the glass fiber), and the length-diameter ratio of the glass fiber is 20:1-5: 1.

The inventor has found through experiments that in the above further preferred embodiment, two parameters of the shaping pulling force and the cooling deformation pressing force of the material are unexpectedly and significantly optimized. The low temperature thermoplastic material and the fastening device of the present invention will thus be more suitable for applications involving stretching, especially stretching to a certain extent or more. This optimized phenomenon is exhibited in the range of 20% to 100% of gel content, particularly in the range of 20% to 70%, and more particularly in the range of 20% to 50%.

It is understood that the aspect ratio is a structural parameter of the glass fiber; but in general it is easier and more straightforward to determine the structural characteristics of the glass fibers by mesh number (length of the glass fibers). The diameter of the glass fiber, which is commonly used in industrial applications, is generally 7 to 13 μm, and after confirming the diameter of the glass fiber as a raw material, those skilled in the art can easily think that a glass fiber having a corresponding aspect ratio can be obtained by specifying a specific mesh number of the glass fiber.

Detailed Description

The materials and effects of the present invention are described in detail below by way of exemplary embodiments. It is noted that certain parameters in the following exemplary embodiments will be used with uniform values (such as the type and amount of cross-linking agent) to facilitate cross-directional comparison of the effect data, but this is not intended to represent that the benefits claimed in this specification cannot be obtained when other types or values recited in the specification are used. The claimed advantageous effects can be achieved by using a certain value or kind within the range described in the specification, and the description is not repeated herein for reasons of space limitation.

Example 1

Preparation of materials

1. Method for preparing material

The material was prepared according to the following steps:

(1) the base material, the filler and the crosslinking agent are stirred to obtain a uniform mixture.

(2) In a double-screw granulator, the mixture is melted, blended and extruded into granules, and the melting temperature is between 60 and 150 ℃.

(3) And (3) rolling and molding the granules in an extrusion rolling device, wherein the processing temperature is between 60 and 150 ℃.

(4) Irradiating the sheet material by a linear accelerator with gamma ray at an irradiation dose of 7KGy, and controlling the irradiation time to obtain the low-temperature thermoplastic material with the required gel content.

2. Gel content determination method

The gel content of the product was determined by the following steps:

weighing a sample with the mass m1, putting the sample into a ground bottle filled with 25mL of toluene, tightly covering the bottle cap, putting the bottle in a constant-temperature oven at 25 ℃ to swell for 48 hours, and taking out the sample. The sample was then extracted for 24 hours and finally the sample was dried in a vacuum oven at 50 ℃ until the mass was constant and the mass was weighed to give a mass m 2. The gel content is Vc m2/m1 × 100%.

Material 1:

base material polycaprolactone (weight average molecular weight 50000). The filler glass fiber (aspect ratio 200:1, i.e. chopped glass fiber) had a filler proportion (i.e. the proportion of filler in the total mass of substrate and filler) of 15%. The dosage of the cross-linking agent triallyl isocyanurate accounts for 0.2 percent of the total mass of the base material and the filler. The product with gel content of 40% is obtained.

Material 2:

base material polycaprolactone (weight average molecular weight 50000). The filler glass fiber (length-diameter ratio 200:1, namely chopped glass fiber) has the filler proportion of 25 percent. The dosage of the cross-linking agent triallyl isocyanurate accounts for 0.2 percent of the total mass of the base material and the filler. The product with gel content of 40% is obtained.

Material 3:

base material polycaprolactone (weight average molecular weight 50000). The filler glass fiber (length-diameter ratio 200:1, namely chopped glass fiber) has the filler proportion of 35 percent. The dosage of the cross-linking agent triallyl isocyanurate accounts for 0.2 percent of the total mass of the base material and the filler. The product with gel content of 40% is obtained.

Material 4:

base material polycaprolactone (weight average molecular weight 50000). Filler glass fiber (length-diameter ratio 50:1), filler proportion is 25%. The dosage of the cross-linking agent triallyl isocyanurate accounts for 0.2 percent of the total mass of the base material and the filler. The product with gel content of 40% is obtained.

Material 5:

base material polycaprolactone (weight average molecular weight 50000). The filler glass fiber (length-diameter ratio 20:1) has a filler proportion of 15%. The dosage of the cross-linking agent triallyl isocyanurate accounts for 0.2 percent of the total mass of the base material and the filler. The product with gel content of 40% is obtained.

Material 6:

base material polycaprolactone (weight average molecular weight 50000). Filler glass fiber (length-diameter ratio 20:1), filler proportion 25%. The dosage of the cross-linking agent triallyl isocyanurate accounts for 0.2 percent of the total mass of the base material and the filler. The product with gel content of 40% is obtained.

Material 7:

base material polycaprolactone (weight average molecular weight 50000). The filler glass fiber (length-diameter ratio 10:1) has a filler proportion of 15%. The dosage of the cross-linking agent triallyl isocyanurate accounts for 0.2 percent of the total mass of the base material and the filler. The product with gel content of 40% is obtained.

Material 8:

base material polycaprolactone (weight average molecular weight 50000). The filler glass fiber (the length-diameter ratio of 20:1 and the length-diameter ratio of 10:1 are mixed), the filler proportion is 15% (the two proportions are 5% and 10% respectively). The dosage of the cross-linking agent triallyl isocyanurate accounts for 0.2 percent of the total mass of the base material and the filler. The product with gel content of 40% is obtained.

Material 9:

base material polycaprolactone (weight average molecular weight 50000). The filler glass fiber (length-diameter ratio 5:1) and the filler proportion is 25 percent. The dosage of the cross-linking agent triallyl isocyanurate accounts for 0.2 percent of the total mass of the base material and the filler. The product with gel content of 40% is obtained.

Material 10:

base material polycaprolactone (weight average molecular weight 50000). The filler glass fiber (length-diameter ratio 2:1) has a filler proportion of 15 percent. The dosage of the cross-linking agent triallyl isocyanurate accounts for 0.2 percent of the total mass of the base material and the filler. The product with gel content of 40% is obtained.

Material 11:

base material polycaprolactone (weight average molecular weight 50000). The filler glass fiber (length-diameter ratio 2:1) has a filler proportion of 35 percent. The dosage of the cross-linking agent triallyl isocyanurate accounts for 0.2 percent of the total mass of the base material and the filler. The product with gel content of 40% is obtained.

Material 12:

base material polycaprolactone (weight average molecular weight 50000). The filler glass fiber (the length-diameter ratio of 5:1 and the length-diameter ratio of 2:1 are mixed), the filler proportion is 25% (the two proportions are respectively 10% and 15%). The dosage of the cross-linking agent triallyl isocyanurate accounts for 0.2 percent of the total mass of the base material and the filler. The product with gel content of 40% is obtained.

Material 13:

base material polycaprolactone (weight average molecular weight 50000). And no filler is added. The cross-linking agent triallyl isocyanurate accounts for 0.2 percent of the mass of the base material. The product with gel content of 40% is obtained.

Material 14:

base material polycaprolactone (weight average molecular weight 50000). Talcum powder (800 mesh) as filler, 25% filler. The dosage of the cross-linking agent triallyl isocyanurate accounts for 0.2 percent of the total mass of the base material and the filler. The product with gel content of 40% is obtained.

Material 15:

base material polycaprolactone (weight average molecular weight 50000). Talcum powder (800 mesh) as filler, 35% filler. The dosage of the cross-linking agent triallyl isocyanurate accounts for 0.2 percent of the total mass of the base material and the filler. The product with gel content of 40% is obtained.

Material 16:

base material polycaprolactone (weight average molecular weight 50000). Mica powder (800 meshes) as filler, and the filler proportion is 25%. The dosage of the cross-linking agent triallyl isocyanurate accounts for 0.2 percent of the total mass of the base material and the filler. The product with gel content of 40% is obtained.

Material 17:

base material polycaprolactone (weight average molecular weight 50000). Filler silica (800 mesh) with a filler proportion of 15%. The dosage of the cross-linking agent triallyl isocyanurate accounts for 0.2 percent of the total mass of the base material and the filler. The product with gel content of 40% is obtained.

Material 18:

base material polycaprolactone (weight average molecular weight 50000). Filler silica (800 mesh) with a filler proportion of 35%. The dosage of the cross-linking agent triallyl isocyanurate accounts for 0.2 percent of the total mass of the base material and the filler. The product with gel content of 40% is obtained.

Second, performance test

1. Flexural Strength test

The low temperature thermoplastic materials prepared above were tested using a universal mechanical testing machine, and the test results are shown in table 1 (results are flexural modulus, in MPa).

TABLE 1 flexural Strength test results

Numbering	1	2	3	4	5	6	7	8	9
										Results	751	942	1251	751	685	761	634	657	642
Numbering	10	11	12	13	14	15	16	17	18
										Results	450	602	627	412	561	612	531	462	570

2. Traction force test and cooling deformation compression force test

The pressure sensor connected with a computer (provided with special software) is arranged below the head of the plaster model, the heated membrane is placed on the face of the plaster model and stretched and shaped downwards, the membrane is fixed on a base which is not connected with the pressure sensor after stretching, and the computer software records the stress condition change condition from the beginning to the complete cooling process of the membrane, and the result is shown in a table 2 (the result unit is N).

TABLE 2 moulding pulling force test results

Numbering	1	2	3	4	5	6	7	8	9
										Pulling force	89	-	-	-	27	31	22	23	24
Force of compression	64	-	-	-	45	39	49	48	47
										Numbering	10	11	12	13	14	15	16	17	18
Pulling force	21	31	28	19	38	44	40	27	48
										Force of compression	99	88	70	120	99	110	94	100	115

Note: materials 2, 3, 4 broke during the test, so there was no test data.

As can be seen from Table 1, the glass fiber has an obvious reinforcing effect on the polycaprolactone low-temperature thermoplastic material, and under the same addition, the glass fiber reinforcing material is superior to a common reinforcing filling material, so that the reinforcing effect is better, and the deformation resistance is stronger. When the material is applied to radiotherapy location and makes the location diaphragm, because the location diaphragm effect is fixed patient's head or parts such as neck chest, prevent that radiotherapy in-process patient from removing, consequently, the resistant deformability of diaphragm material is better, and then the fixity after moulding on patient's health is better, adds the fixed precision that glass fiber material can show improvement diaphragm.

As can be seen from Table 2, the cooling deformation compression force of the radiotherapy positioning membrane prepared by the glass fiber is obviously lower than that of the low-temperature radiotherapy positioning membrane prepared by pure polycaprolactone and other common reinforced filling materials. The lower the cooling compression, the more comfortable the user is in the clinic.

Therefore, the fixing device prepared by the material has higher bending modulus and lower cooling deformation compression force compared with a low-temperature radiotherapy positioning membrane prepared by pure polycaprolactone and other common reinforced filling materials. Namely, the low-temperature thermoplastic material prepared by the invention has smaller contractility after forming, better comfort and better fixing strength, thereby being more suitable for hospitals or other radiotherapy units and being matched with three-dimensional conformal radiotherapy instruments for use in tumor operations.

The radiotherapy positioning membrane prepared by different formula materials has different pulling forces during shaping, and for glass fiber products, the larger the length-diameter ratio of the glass fiber is, the larger the shaping pulling force is. The product prepared from the chopped glass fiber is broken due to excessive pulling force, and the greater the pulling force for shaping in clinical application, the lower the comfort of patients. The glass fiber with the length-diameter ratio of more than 20:1 is applied, the radiotherapy positioning membrane prepared by the glass fiber has serious discomfort through testing, and the material has low elongation at break and is easy to break.

However, the inventors have found that in applications involving stretching, particularly where stretching to a greater degree is required (e.g. where it is desired to stretch-form a softened material), a proportion of the product breaks and is unusable. Through comparative experiments based on various parameters, the inventors found that this is mainly caused by using long glass fibers or short glass fibers commonly used in the art.

Generally, to obtain higher strength, those skilled in the art will prefer to use glass fibers having a high aspect ratio, such as chopped glass fibers. The greater the moulding pull in clinical applications, the less comfortable it is for the user (patient). As can be seen from table 2, when the glass fibers (including chopped glass fibers) with the length-diameter ratio of 20:1 or 5:1 are used, the tension of the radiotherapy positioning film prepared from the glass fibers is too large, so that a user feels severe discomfort when the glass fibers are used in an application process requiring stretching, particularly when the glass fibers are required to be stretched to a certain extent, and the material has too low elongation at break and is easy to break. However, if the aspect ratio of the glass fibers is controlled to be 20:1 to 5:1 and the amount thereof is further controlled to be 15% to 25%, surprisingly, the resulting high temperature thermoplastic material has a significantly reduced compressive and tensile forces while maintaining a high flexural modulus, greatly improving the comfort to the user. If the amount is outside the range of 15-25% or the aspect ratio is outside the range of 20:1-5:1, the pulling force or the pressing force of the obtained product is similar to that of chopped glass fiber, and the product can be broken when more than a certain degree of stretching is needed; the compression force is even higher with further reduction of aspect ratio than with chopped glass fibers (such as materials 10 and 11).

Therefore, as a further preferable embodiment of the present invention, the mass ratio of the polycaprolactone to the glass fiber is 75:25-85:15 (i.e. the glass fiber accounts for 15% -25% of the total mass of the polycaprolactone and the glass fiber), and the length-diameter ratio of the glass fiber is 20:1-5: 1. This preferred solution will allow to greatly increase the range of applications of the above-mentioned low temperature thermoplastic material and of the fastening device, in particular applications involving stretching, more particularly applications requiring stretching to a certain extent or more.

Example 2

Preparation of materials

1. Method for preparing material

The material was prepared according to the following steps:

(4) Irradiating the sheet material by a linear accelerator with gamma ray at an irradiation dose of 4KGy, and controlling the irradiation time to obtain the low-temperature thermoplastic material with the required gel content.

2. Gel content determination method

The gel content was measured in the same manner as in example 1.

Material 19:

substrate polycaprolactone (weight average molecular weight 40000). The filler glass fiber (the length-diameter ratio of 20:1 and the length-diameter ratio of 10:1 are mixed), the filler proportion is 25% (the two proportions are respectively 10% and 15%). The dosage of the cross-linking agent triallyl isocyanurate accounts for 0.2 percent of the total mass of the base material and the filler. The product was obtained with a gel content of 30%.

Material 20:

substrate polycaprolactone (weight average molecular weight 80000). The filler glass fiber (the length-diameter ratio of 20:1 and the length-diameter ratio of 10:1 are mixed), the filler proportion is 25% (the two proportions are respectively 10% and 15%). The dosage of the cross-linking agent triallyl isocyanurate accounts for 0.2 percent of the total mass of the base material and the filler. The product was obtained with a gel content of 30%.

Second, performance test

The test method was the same as in example 1, and the results are shown in Table 3.

Table 3 example 2 test results

Example 3

Preparation of materials

1. Method for preparing material

The material was prepared according to the following steps:

(4) Irradiating the sheet material with gamma rays through a linear accelerator, and controlling the irradiation time to obtain the low-temperature thermoplastic material with the required gel content.

2. Gel content determination method

The gel content was measured in the same manner as in example 1.

Material 21:

base material polycaprolactone (weight average molecular weight 50000). The filler glass fiber (the length-diameter ratio of 20:1 and the length-diameter ratio of 10:1 are mixed), the filler proportion is 25% (the two proportions are respectively 10% and 15%). The dosage of the cross-linking agent triallyl isocyanurate accounts for 0.05 percent of the total mass of the base material and the filler. The irradiation dose was 5KGy, and a product having a gel content of 20% was obtained.

Material 22:

base material polycaprolactone (weight average molecular weight 50000). The filler glass fiber (the length-diameter ratio of 20:1 and the length-diameter ratio of 10:1 are mixed), the filler proportion is 25% (the two proportions are respectively 10% and 15%). The cross-linking agent triallyl isocyanurate accounts for 5 percent of the total mass of the base material and the filler. The irradiation dose was 5KGy, and a product having a gel content of 50% was obtained.

Material 23:

base material polycaprolactone (weight average molecular weight 50000). The filler glass fiber (the length-diameter ratio of 20:1 and the length-diameter ratio of 10:1 are mixed), the filler proportion is 25% (the two proportions are respectively 10% and 15%). The cross-linking agent triallyl isocyanurate accounts for 5 percent of the total mass of the base material and the filler. The irradiation dose was 10kGy, and a product with a gel content of 70% was obtained.

Material 24:

base material polycaprolactone (weight average molecular weight 50000). The filler glass fiber (the length-diameter ratio of 20:1 and the length-diameter ratio of 10:1 are mixed), the filler proportion is 25% (the two proportions are respectively 10% and 15%). The cross-linking agent triallyl isocyanurate accounts for 5 percent of the total mass of the base material and the filler. The irradiation dose was 30kGy, and a product with 100% gel content was obtained.

Second, performance test

The test method was the same as in example 1, and the results are shown in Table 4.

Table 4 example 3 test results

Claims

1. A low-temperature thermoplastic material is characterized in that the low-temperature thermoplastic material is composed of polycaprolactone and glass fiber, and the gel content is greater than or equal to 20%; wherein the mass ratio of the polycaprolactone to the glass fiber is 65:35-95: 5.

2. A cryogenic thermoplastic material according to claim 1, wherein the mass ratio of polycaprolactone to glass fibres is from 75:25 to 85:15 and the aspect ratio of the glass fibres is from 20:1 to 5: 1.

3. A method for preparing a cryogenic thermoplastic material, comprising the steps of:

4. The method of claim 3, wherein the cross-linking agent is selected from the group consisting of triallylisocyanurate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, ethylene dimethacrylate, in an amount of 0.05% to 5% of the total mass of polycaprolactone and glass fiber; the crosslinking process in the step (2) is irradiation crosslinking.

5. The method as claimed in claim 3, wherein the polycaprolactone of step (1) has a weight average molecular weight of 40000-.

6. The method of any of claims 3 to 5, wherein the mass ratio of polycaprolactone to glass fiber is 75:25 to 85:15, and the aspect ratio of glass fiber is 20:1 to 5: 1.

7. Use of the cryogenic thermoplastic material according to claim 1 or 2 for the preparation of a device for the fixation of a human site or joint.

8. Use of a low temperature thermoplastic material obtainable by a process according to any one of claims 3 to 6 for the preparation of a device for fixation of a human site or joint.

9. A device for immobilising a human region or joint, wherein the body of the device is made of a low temperature thermoplastic material as claimed in claim 1 or 2 or as prepared by a method as claimed in any of claims 3 to 6.

10. Use of a device according to claim 9 for radiotherapy.