A low-temperature thermoplastic composition and the low-temperature thermoplastic material made therefrom

Abstract

This invention discloses a low-temperature thermoplastic composition and the low-temperature thermoplastic material made therefrom, as well as its applications, relating to the field of medical materials technology. The low-temperature thermoplastic composition mainly comprises the following components: thermoplastic resin, reinforcing filler, and radiation crosslinking agent; the thermoplastic resin includes polyurethane, and each 100 parts of the low-temperature thermoplastic composition contains at least 27 parts of a first polyurethane with a flow start temperature of 50-95°C and an open time of at least 6 minutes. Through the selection of polyurethane and the combination of reinforcing filler, the low-temperature thermoplastic composition enables the low-temperature thermoplastic material to have lower shrinkage and a longer operating time, allowing the low-temperature thermoplastic material prepared from the composition to be used for fixation of parts with higher operating time requirements.

Description

Technical Field

[0001] This invention relates to the field of medical materials technology, and more specifically, to a low-temperature thermoplastic composition and the low-temperature thermoplastic material made therefrom. Background Technology

[0002] Common low-temperature thermoplastic materials are made primarily from polycaprolactone (PVC) polymers with added additives. Their characteristic is that they soften when heated to around 65°C and can be molded into any shape, while retaining the rigidity of polyethylene upon cooling to room temperature. Based on this characteristic, the material can be used for precise positioning during radiotherapy in cancer patients and for immobilizing the limbs or trunk during rehabilitation and orthopedics. Currently, PVC-based low-temperature thermoplastic materials are practically used in the manufacture of radiotherapy positioning membranes and in the field of rehabilitation and orthopedics. When performing radiotherapy on cancer lesions, it is essential to first immobilize the lesion site, typically using PVC-based radiotherapy positioning membranes. The shrinkage of the radiotherapy positioning membrane after molding can create pressure on the patient; the greater the shrinkage, the more uncomfortable the patient. Generally, the smaller the shrinkage force of the membrane, the better. The technical solution proposed in Chinese patent CN101698743A uses polyurethane with a melting point of 50℃~70℃ to partially or completely replace polycaprolactone, which can effectively reduce shrinkage. However, the product has low flexural strength. If its flexural strength can be improved, the fixation effect of the diaphragm will be better. In the prior art, fillers are added to improve the flexural strength of low-temperature thermoplastic materials. Chinese patent CN112375352A discloses the addition of glass fibers of special size to increase the strength of polycaprolactone materials, while also reducing the shrinkage of polycaprolactone films. Q-FIX in the United States uses Kevlar fibers to increase the strength of polycaprolactone materials, while also reducing the shrinkage of polycaprolactone films. Although both can effectively increase the flexural strength of polycaprolactone materials and reduce shrinkage, the drawback is that Kevlar fibers and glass fibers can cause skin allergies in some patients, causing itching, rashes, and other discomfort. Chinese patent CN112480616A discloses the use of melamine salts to enhance the flexural strength of polycaprolactone (PVC) materials while simultaneously reducing the shrinkage force of PVC membranes. Although the shrinkage force problem is solved, a new issue arises: the operation time of PVC radiotherapy membranes with added melamine salts is significantly shorter than that without melamine salts, especially for large-area fixation (such as the head, neck, shoulder, waist, and hip). The operation time of PVC membranes without melamine salts is already very limited; with melamine salts, the operation time is practically insufficient for large-area fixation. Therefore, further improvements to the membrane's performance are desired. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of existing raw materials for preparing polycaprolactone and polyurethane-type low-temperature thermoplastic materials, and to provide a new low-temperature thermoplastic composition.

[0004] Another object of the present invention is to provide a low-temperature thermoplastic material.

[0005] Another object of the present invention is to provide a method for preparing a low-temperature thermoplastic material.

[0006] Another objective of this invention is to provide an application of a low-temperature thermoplastic material in radiotherapy positioning films and rehabilitation orthopedic products.

[0007] The above-mentioned objective of this invention is achieved through the following technical solution:

[0008] The low-temperature thermoplastic composition mainly consists of the following components:

[0009] Thermoplastic resin, reinforcing filler, radiation crosslinking aid;

[0010] The thermoplastic resin contains polyurethane, and each 100 parts of the low-temperature thermoplastic composition contains at least 27 parts of a first polyurethane with a flow start temperature of 50-95°C and an open time of 6 minutes or more.

[0011] In this invention, the open time is determined by testing according to HG / T3716-2003 [Determination of Open Time of Hot Melt Adhesives].

[0012] In this invention, the flow initiation temperature is determined by temperature scanning using a capillary rheometer / melt indexer.

[0013] Testing equipment: capillary rheometer or melt flow indexer.

[0014] Test principle: At different temperature points, the extrusion rate (apparent viscosity) of the gel sample through a standard die under a fixed load is measured.

[0015] Judgment criterion: Plot the apparent viscosity against temperature. The temperature corresponding to the inflection point where the viscosity begins to decrease rapidly is the flow initiation temperature.

[0016] The inventors discovered that by adding a first polyurethane with a specific open time and controlling its content in the composition, the shortcomings of the short operating time of low-temperature thermoplastic materials can be compensated.

[0017] Preferably, the low-temperature thermoplastic composition further contains polycaprolactone in an amount not exceeding 68% of the total mass of the thermoplastic resin in the low-temperature thermoplastic composition.

[0018] The addition of polycaprolactone mainly reduces the irradiation dose required for crosslinking of low-temperature thermoplastic compositions.

[0019] In addition, unlike polyurethane, polycaprolactone has a relatively simple structure, so its open time is relatively stable. The open time of polycaprolactone from different manufacturers or models is basically maintained at 3 minutes.

[0020] Preferably, the thermoplastic resin further contains no more than 53% by weight of a second polyurethane, wherein the flow start temperature of the second polyurethane is 50-95°C and the open time is less than 6 minutes.

[0021] The properties of low-temperature thermoplastic materials can be further adjusted by adding a second polyurethane.

[0022] Preferably, the reinforcing filler is selected from at least one of melamine salt, attapulgite, or POM. More preferably, it is attapulgite. The inventors unexpectedly discovered that attapulgite has a smaller impact on the operating time of the composition compared to melamine salt and POM; that is, the composition with attapulgite as the reinforcing filler has the longest operating time among the three.

[0023] Generally, the reinforcing filler accounts for 10-30% of the mass of the low-temperature thermoplastic composition. Adding reinforcing filler can significantly improve the flexural strength of the low-temperature thermoplastic composition, but it generally has a negative impact on the operating time. More preferably, the reinforcing filler accounts for 15-25% of the mass of the low-temperature thermoplastic composition.

[0024] In this field, surface modifiers are generally used to improve the dispersibility of attapulgite. Commonly used surface modifiers include silane coupling agents. The amount of surface modifier used is generally 1-5% of the weight of the attapulgite.

[0025] The purpose of the irradiation crosslinking aid is to improve the crosslinking effect of the low-temperature polyurethane during the irradiation process, thereby achieving the desired gel content. In this invention, the irradiation crosslinking aid includes, but is not limited to, one or more of the following: triallyl isocyanurate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, or ethylene diisobutylene ester.

[0026] The polyurethane used in this invention, with a flow start temperature of 50~95°C, can be a commercially available product, such as polyurethane hot melt adhesive granules, or it can be prepared by itself according to a known method, such as the method described in CN101760165A.

[0027] The low-temperature thermoplastic material of the present invention includes the following steps: the low-temperature thermoplastic composition is melt-blended and extruded, and then subjected to irradiation treatment to obtain the low-temperature thermoplastic material.

[0028] The melt-blending extrusion molding process includes: extruding uniform materials into sheets of the required thickness using an extruder.

[0029] The specific parameters for melt blending extrusion can be referenced as follows: the temperature of the feeding section should be controlled at room temperature to 50℃, the temperature of the compression section at 90 to 110℃, the temperature of the homogenization section at 100 to 120℃, and the temperature of the die head and orifice section at 90 to 105℃. The screw speed is preferably 0.3 to 0.6 m / min.

[0030] Other plastic molding machines can also be used to produce sheets of the required thickness.

[0031] Preferably, the gel content of the low-temperature thermoplastic material is not less than 20%.

[0032] More preferably, the gel content of the low-temperature thermoplastic material is not less than 30%.

[0033] More preferably, the gel content of the low-temperature thermoplastic material is not higher than 50%.

[0034] More preferably, the gel content of the low-temperature thermoplastic material is not higher than 35%.

[0035] In this field, "gel content" refers to the content of gel substances in low-temperature thermoplastic materials, reflecting the degree of irradiation crosslinking. Existing methods can be referenced, such as those described in CN112480616A.

[0036] Specifically, the method for detecting the gel content of the low-temperature thermoplastic material is as follows: Weigh a sample with a mass of m1, place the sample in a ground glass bottle containing 25 mL of toluene, tighten the cap, and place it in a constant temperature oven at 25°C for 48 hours to swell. Then, extract the sample in toluene for 24 hours. Finally, dry the sample in a vacuum drying oven at 50°C until its mass is constant, and weigh it again to obtain a sample with a mass of m2. The gel content is then calculated using the formula: V c = m2 / m1×100%, the gel content Vc is calculated.

[0037] The irradiation dose required to form the above-mentioned gel content in thermoplastic materials is mainly determined by the type of thermoplastic resin. For example, a higher polyurethane content often requires a larger irradiation dose, while increasing the proportion of polycaprolactone can reduce the irradiation dose required to obtain the target gel content.

[0038] In this invention, the flexural modulus of the low-temperature thermoplastic material is ≥700MPa, the shrinkage force is ≤60N, and the operating time is ≥60 seconds.

[0039] In comparison, while the operating time of pure polycaprolactone is also 60 seconds, its shrinkage force is over 100N. Melamine salt-modified polycaprolactone, although the addition of melamine salt significantly reduces its shrinkage force to around 70N, also significantly reduces its operating time to around 50 seconds.

[0040] As a further embodiment, the irradiation treatment uses high-energy rays from a linear accelerator or cobalt-60.

[0041] Application of the low-temperature thermoplastic material in radiotherapy positioning films and rehabilitation orthopedic products.

[0042] When using radiotherapy membranes to fix large areas such as the head, neck, shoulders, waist, and hips, the membranes are large and have many slots that need to be fixed to the base. The 60-second operation time for pure polycaprolactone membranes is already very tight, and the operation time for melamine salt-reinforced polycaprolactone membranes is even shorter, making them practically unusable in clinical practice.

[0043] Compared with the prior art, the beneficial effects of the present invention are:

[0044] This invention provides a low-temperature thermoplastic composition. By selecting polyurethane and combining reinforcing fillers, the low-temperature thermoplastic material has higher flexural strength, lower shrinkage, and longer operating time, enabling the low-temperature thermoplastic material prepared by the low-temperature thermoplastic composition to be used for fixing parts with higher operating time requirements. Detailed Implementation

[0045] The present invention will be further described below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise stated, the raw materials and reagents used in the embodiments of the present invention are commercially available conventional raw materials and reagents.

[0046] In the embodiments, the polyurethane involved is sourced from the following sources:

[0047] Polyurethane A: Flow start temperature is 65±10℃, purchased from Taiwan FreeRadical PMCo., Ltd., China, model number H6010, batch 1. According to HG / T3716-2003 test, the open time of this batch of polyurethane is 6 minutes.

[0048] Polyurethane B: Flow start temperature is 85±10℃, purchased from Taiwan FreeRadical PMCo., Ltd., China, model number 8510F, batch 1. According to HG / T3716-2003 test, the open time of this batch of polyurethane is 8 minutes.

[0049] Polyurethane C: Flow start temperature is 60±10℃, purchased from Taiwan FreeRadical PMCo., Ltd., China, model H1150; batch 1, according to HG / T3716-2003 test, the open time of this batch of polyurethane is 25 minutes.

[0050] Polyurethane D: Flow start temperature is 65±10℃, purchased from Taiwan FreeRadical PMCo., Ltd., China, model H6010, batch 2. According to HG / T3716-2003 test, the open time of this batch of polyurethane is 4 minutes.

[0051] Polyurethane E: Flow start temperature is 65±10℃, purchased from Taiwan FreeRadical PMCo., Ltd., China, model number H7020, batch 1, according to HG / T3716-2003 test, the open time of this batch of polyurethane is 4 minutes.

[0052] Polycaprolactone: Purchased from Hunan Juren Chemical New Material Technology Co., Ltd. in China, model PCL-6500, tested according to HG / T3716-2003, batch 1, open time 3 minutes.

[0053] Melamine salt, melamine cyanurate, 800 mesh, Shouguang Puer Chemical Co., Ltd.

[0054] Attapulgite, 800 mesh, from Yanguo Mineral Products Processing Plant, Lingshou County.

[0055] Polyoxymethylene, Yuntianhua, self-ground powder, 800 mesh.

[0056] The attapulgite clay is dried and surface-treated with 2% (by weight of 2%) of silane coupling agent KH550.

[0057] The irradiation crosslinking aid is triallyl isocyanurate.

[0058] The formulations of each embodiment and comparative example are shown in Table 1. The preparation methods of the low-temperature thermoplastic materials in each embodiment are as follows:

[0059] The mixtures were thoroughly mixed according to the formulations in Table 1, extruded and granulated using a twin-screw extruder, and then extruded into sheets. The sheets were then subjected to irradiation crosslinking using a linear accelerator to obtain the low-temperature thermoplastic material. Due to variations in polycaprolactone content, the intensity of the irradiation crosslinking was controlled differently. Based on the polycaprolactone content, Comparative Examples 1 and 2 were irradiated at 5-6 kGy, Examples 3 and 6 at 7-8 kGy, and the remaining examples and comparative examples were irradiated at 12-13 kGy. The gel content of the prepared low-temperature thermoplastic material was above 20%, and is not listed separately in the table.

[0060] Performance testing:

[0061] Bending strength test

[0062] The low-temperature thermoplastic material prepared above was tested using a universal mechanical testing machine (the result is the flexural modulus, in MPa).

[0063] Contraction force test

[0064] A pressure sensor connected to a computer (with dedicated software) was placed below the head of the plaster mannequin. A heated diaphragm was then placed on the face of the plaster mannequin and stretched downwards to shape it. After stretching, the diaphragm was fixed to a base that was not connected to the pressure sensor. The computer software recorded the changes in the force from the beginning until the diaphragm was completely cooled. The results are shown in Table 1 (the unit of the results is N).

[0065] Operation time test

[0066] (1) Cut several 2x10 cm strips from the irradiated low-temperature thermoplastic sheets of each formula.

[0067] (2) Set the oven temperature to 75°C, place each formulation sample strip on polytetrafluoroethylene cloth, and bake in the oven at 75°C for 15 minutes.

[0068] Start timing, setting the timing intervals to 50 seconds, 51 seconds, 52 seconds... up to 65 seconds. When the corresponding time is reached, remove the sample strip and stretch it to 35 centimeters. If the sample strip cannot be stretched to 35 centimeters, the time from the previous time point to the start of timing is the working time of the sample strip.

[0069] Table 1 (The amount of each component is in parts by weight)

[0070]

[0071] As can be seen from Table 1, the operating time of the low-temperature thermoplastic composition in the embodiments of the present invention is significantly extended, and the higher the polyurethane content in the low-temperature thermoplastic composition, the lower the shrinkage force. A comparison of Examples 4 and 5 with Examples 1 and 2 shows that using attapulgite as a reinforcing filler enables the low-temperature thermoplastic composition to have a longer operating time compared to other reinforcing fillers.

[0072] The above embodiments of the present invention are merely examples for clearly illustrating the present invention and are not intended to limit the implementation of the present invention. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively describe all possible implementations here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A low-temperature thermoplastic composition, characterized in that, It is mainly composed of the following components: Thermoplastic resin, reinforcing filler, radiation crosslinking aid; The thermoplastic resin contains polyurethane, and each 100 parts of the low-temperature thermoplastic composition contains at least 27 parts of a first polyurethane with a flow start temperature of 50~95°C and an open time of more than 6 minutes. The first polyurethane is a polyurethane from Free Radical Co., Ltd. in Taiwan, with the model number H6010, 8510F or H1150; The thermoplastic resin also contains polycaprolactone in an amount not exceeding 68% of the total mass of the thermoplastic resin. The reinforcing filler accounts for 10-30% of the mass of the low-temperature thermoplastic composition; The reinforcing filler is selected from at least one of melamine salt, attapulgite, or POM.

2. The low-temperature thermoplastic composition according to claim 1, characterized in that, The thermoplastic resin further contains no more than 53% by weight of a second polyurethane, wherein the flow start temperature of the second polyurethane is 50-95°C and the open time is less than 6 minutes.

3. The low-temperature thermoplastic composition according to claim 1, characterized in that, The attapulgite clay is also treated with surfactants.

4. The low-temperature thermoplastic composition according to any one of claims 1 to 3, characterized in that, The irradiation crosslinking aid is selected from one or more of triallyl isocyanurate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, or pentaerythritol triacrylate.

5. A low-temperature thermoplastic material, characterized in that, The process includes the following steps: melting and extruding the low-temperature thermoplastic composition according to any one of claims 1 to 4, followed by irradiation treatment to obtain the low-temperature thermoplastic material.

6. The low-temperature thermoplastic material according to claim 5, characterized in that, The gel content of the low-temperature thermoplastic material is not less than 20%.

7. The application of the low-temperature thermoplastic material as described in claim 5 or 6 in radiotherapy positioning films and rehabilitation orthopedic products.

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