expanded thermoplastic elastomer particles

Technical field

The present invention relates to a non-pneumatic tire, a method of producing a non- pneumatic tire, and preferably use of the non-pneumatic tire in a low-speed vehicle such as a bicycle, a monocycle, a trolley, a construction vehicle, a lawnmower, a golf trolley, a haul truck, a wheelchair, an electric scooter, a scooter, and an electric bicycle.

Background of arts

Pneumatic tires have been widely used in bicycles, cars, trucks, airplanes, etc. In these ap- plications, travel quality and comfort are important parts of vehicle performance. However, pneumatic tires are very sensitive to cracks, punctures and/or other damage that can lead to leak of tire. Tires need to be repaired or replaced when there is a leak, resulting in more finan- cial burden. More seriously, if tire leaks abruptly, such as bursting, it can cause safety problems.

As an alternative, non-pneumatic tires appeared. Unlike pneumatic tires, non-pneumatic tires do not suffer from leaks. A variety of non-pneumatic tires have been developed.

CN1715041A discloses a non-pneumatic tire and a method of manufacturing the same, wherein the filler component comprises a polyurethane, which has a Shore A hardness of about 68 to about 75.

CN106188493A discloses a composition for expanded polyurethane tire, wherein tires made of the composition have a density of 400-500kg/m ³ and a Shore A hardness of 65-90.

WO2017/039451 A1 discloses a wheel assembly comprising a non-pneumatic tire wherein the non-pneumatic tire is made of a foamed polymer, such as expanded thermoplastic polyure- thanes (E-TPU).

CN105939870A discloses a polyurethane-filled tire made of a porous polyurethane or poly- urethane-urea elastic material having a Shore A hardness of 45-80 as measured according to ASTM D2240 and a rebound resilience of 40-70% as measured according to ASTM D3574.

CN101583656A discloses a hybrid material comprising a matrix of polyurethane and foamed particles of thermoplastic polyurethane comprised therein and also a process for pro- ducing such hybrid materials and the use of these hybrid materials as floor covering, bicycle saddles, upholstery and shoe soles.

US 2010/0122758 A1 discloses a tire comprising a foam part made of a rubber or plastic material and a hollow elastic part present in the foam part, the hollow elastic part being made of rubber or thermoelastic rubber.

CN105346332A discloses a tire, wherein the tire casing is made of polyurethane material and the tire core is made by molding E-TPU particles.

CN10430941 1A discloses a thermoplastic polyurethane low load tire comprising a surface layer for direct contact with the ground and an inner layer located inside the surface layer, wherein the surface layer has a higher hardness than the inner layer, and the surface layer and the inner layer are formed by molding E-TPU particles.

CN104290539A discloses a tire in which numerous E-TPU elastic closed cell particles are placed in the space formed by the tire casing and the wheel hub, and are adhered together by using an adhesive or a surface hot melt process.

Although a wide variety of non-pneumatic tires have been developed, these non-pneumatic tires generally have the disadvantage of being heavy and poor in rebound resilience compared to pneumatic tires. Therefore, there is still a need to further provide a non-pneumatic tire with light weight and good rebound resilience.

Invention summary

The present invention provides a non-pneumatic tire comprising 60 to 90wt% of a polyure- thane matrix and 10 to 40wt% of expanded thermoplastic elastomer particles.

The present invention also provides a method of producing a non-pneumatic tire compris- ing the steps of:

(1 ) placing expanded thermoplastic elastomer particles in a mold;

(2) injecting a polyurethane matrix into the mold and curing; and

(3) demoulding.

In addition, the present invention provides use of the non-pneumatic tire in a vehicle, pref- erably a low-speed vehicle such as a bicycle, a monocycle, a trolley, a construction vehicle, a lawnmower, a golf trolley, a haul truck, a wheelchair, an electric scooter, a scooter, and an elec- tric bicycle.

The non-pneumatic tire of the invention has the advantages of one or more of light weight, high rebound resilience and good cushioning effect.

Brief description of the drawings

Figure 1 is a cross-sectional view of a non-pneumatic tire according to the present inven- tion (Example 1), in which E-TPU particles are dispersed in a polyurethane matrix.

Fig. 2 is a cross-sectional view of a dual-density integrated tire according to the present in- vention (Example 3), in which the double-density integrated tire comprises a textured outer tire portion (deep-colored portion) and an inner tire portion (light-colored portion).

Embodiments

In one embodiment of the present invention, there is provided a non-pneumatic tire corn- prising 60 to 90wt% of a polyurethane matrix and 10 to 40wt% of expanded thermoplastic elas- tomer particles. Preferably, the non-pneumatic tire comprises 80 to 90wt% of a polyurethane matrix and 10 to 20wt% of expanded thermoplastic elastomer particles.

The non-pneumatic tire has a Shore A hardness of 40-90, preferably 54-56.

The non-pneumatic tire has a rebound resilience of 45-65%, preferably 50-60%.

The non-pneumatic tire has a density of 300-900 kg/m ³ , preferably 450-600 kg/m ³ . The ex- panded thermoplastic elastomer particles have a density of 200-300 kg/m ³ .

In one embodiment of the invention, the expanded thermoplastic elastomer particles have a diameter of 1 to 15 mm, preferably 4 to 7 mm, and are preferably spherical or oval. In the case of non-spherical shapes, such as oval particles, the diameter is in terms of the long axis.

Polyurethane matrix

According to the invention, the polyurethane matrix is prepared, for example, by reaction of an isocyanate with an isocyanate-reactive compound having a number molecular weight of 500 to 10,000 optionally with a chain extender, optionally in the presence of a catalyst and/or cus- tomary auxiliaries and/or additives.

As isocyanates , it is possible to use aliphatic, alicyclic, araliphatic and/or aromatic isocya- nates and/or isocyanate prepolymers, preferably diisocyanates such as tri-, tetra-, penta-, hexa-, hepta- and/or octa-methylene diisocyanate, 2-methylpentamethylene-1 ,5-diisocyanate, 2- ethylbutylene-1 ,4-diisocyanate, pentamethylene-1 ,5-diisocyanate, butylene-1 ,4-diisocyanate, 1- isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate, IPDI), 1 ,4- and/or 1 ,3-bis (isocyanatomethyl) cyclohexane (HXDI), cyclohexane-1 ,4-diisocyanate, 1- methylcyclohexane-2,4- and/or 2,6-diisocyanates, and/or dicyclohexylmethane-4,4'-, 2,4'- and 2,2'-diisocyanates, diphenylmethane diisocyanate such as diphenylmethane-2,2'-, 2,4'- and/or 4,4'-diisocyanate (MDI), naphthylene-1 ,5-diisocyanate (NDI), tolylene-2,4- and/or 2,6- diisocyanate (TDI), 3,3 ' -dimethyldiphenyl diisocyanate, 1 ,2-diphenylethane diisocyanate, and/or phenylene diisocyanate.

As isocyanate-reactive compounds , it is possible to use isocyanate-reactive compounds, such as polyester polyols, polyether polyols and/or polycarbonate diols, and mixtures thereof, which are usually classified under the term "polyol" and have a number average molecular weight of 500 to 8,000g/mol, preferably 600 to 6,000 g/mol, and preferably have an average functionality of 1.8 to 3.3, in particular 2.0 to 3.0.

As chain extenders, it is possible to use aliphatic, araliphatic, aromatic and/or alicyclic compounds having a number molecular weight of from 50 to 499, preferably bifunctional corn- pounds, such as diamines and/or alkanediols having 2 to 10 carbon atoms, in particular 1 ,4- butanediol, 1 ,6-hexanediol, and/or dialkylene glycols, trialkylene glycols , Tetra alkylene glycols, pentaalkylene glycols, hexaalkylene glycols, heptaalkylene glycols, octaalkylene glycols, nonaalkylene glycols and/or decaalkylene glycols having 3 to 10 carbon atoms, preferably the corresponding oligopropylene glycol and/or polypropylene glycol, but also mixtures of these chain extenders.

As a suitable catalyst for promoting the reaction between NCO groups of the isocyanate and the hydroxyl groups, tertiary amines such as amine gel type catalysts, triethylamine, dime- thylcyclohexylamine, N-methylmorpholine, N,N'-dimethylpiperazine, 2- (dimethylaminoethoxy) ethanol, diazabicyclo [2.2.2] octane and the like, and organometallic compounds such as titan- ates, iron compounds such as acetyl Iron (III) pyruvate, tin compounds such as tin diacetate, tin dioctoate, tin dilaurate, or dialkyl tin salts of aliphatic carboxylic acids such as dibutyltin diace- tate, dibutyltin dilaurate and the like can be used. The catalyst is usually used in an amount of 0.0001-4.0 parts by weight based on 100 parts by weight of the weight of the polyurethane ma- trix.

In addition to the catalysts, customary auxiliaries and/or additives may also be added. Ex- amples which may be mentioned comprise foaming agents, foam stabilizers, surface-active substances, fillers, flame retardants, nucleating agents, oxidation stabilizers, lubricants and mold-release agents, dyes , pigments, reinforcing materials, thickener, and plasticizers.

This reaction can be carried out under conventional index, preferably from 60 to 120, par- ticularly preferably from 80 to 1 10. The index is defined as the ratio of the total number of isocy- anate groups to the isocyanate-reactive groups (e.g. active hydrogen atoms) used in the reac- tion.

The polyurethane matrix can be in the form of a foam or compacted elastomer.

Expanded thermoplastic elastomer particles

In embodiments of the present invention, the expanded thermoplastic elastomer particles comprise expanded (i.e. formed) thermoplastic polyurethane particles; expanded thermoplastic polyester ether particles; expanded thermoplastic polyether ester particles; expanded thermo- plastic polyether amide particles; expanded thermoplastic polyolefin particles such as expanded thermoplastic polyethylene vinyl acetate particles, expanded thermoplastic polyethylene propyl- ene diene particles, expanded thermoplastic polypropylene particles, expanded thermoplastic styrene block copolymer particles; and mixtures thereof.

Preferably, the expanded thermoplastic elastomer particles are expanded thermoplastic polyurethane (E-TPU) particles.

The expanded thermoplastic polyurethane particles can be produced from thermoplastic polyurethane by suspension or extrusion methods known to those skilled in the art and are de- scribed in the above documents. Among these methods, the expanded thermoplastic polyure- thane particles can be obtained directly or indirectly.

In the suspension process, the particulate thermoplastic polyurethane is heated in a closed reactor with water, suspending agent and foaming agent to above the softening temperature of the particulate material. The polymer particles here are impregnated with a foaming agent. One possibility is to cool the hot suspension, then the particles harden in the presence of a foaming agent and the reactor is depressurized. The resultant expandable particles containing a foaming agent are foamed by heating in a subsequent step to obtain foamed particles. In another alter- native, the hot suspension may be suddenly depressurized without cooling (explosion expan- sion process), so the softening particles containing a foaming agent are immediately foamed to produce foamed particles, see, for example, WO 94/20568. In the extrusion process, the thermoplastic polyurethane is melt and mixed in an extruder with a foaming agent introduced into the extruder. The mixture containing the foaming agent is extruded and pelletized under pressure and temperature such that the particulate thermoplastic polyurethane material is not foamed (expanded), which can be achieved, for example, by using granulator under water that is operated at a water pressure in excess of 2 bars. This produces expandable particles containing a foaming agent, and is foamed by heating in a subsequent step to obtain foamed particles. Alternatively, it is also possible to extrude and granulate the mixture without using super atmospheric pressure. In this method, molten strand foam and foamed particles are obtained by pelletization.

The present invention also provides a method of producing a non-pneumatic tire compris- ing:

(1 ) placing expanded thermoplastic elastomer particles in a mold;

(2) injecting a polyurethane matrix into the mold and curing; and

(3) demoulding.

The invention also relates to the use of a non-pneumatic tire in a vehicle, preferably a low- speed vehicle such as a vehicle having a speed of less than 40km/h, preferably less than 30km/h. The vehicles include a bicycle, a monocycle, a trolley, a construction vehicle, a lawnmower, a golf trolley, a haul truck, a wheelchair, an electric scooter, a scooter, and an elec- tric bicycle.

Examples

The invention is illustrated in conjunction with the following examples and figures, which are for illustrative purposes only and should not be construed as limiting the scope of the invention.

The starting materials used in the examples are as follows:

Polyol-A: polyether polyol with a number average molecular weight of 6,000, a functionality of 3 and a hydroxyl value of about 28 mg KOH/g, obtained from Tianjin Petrochemical Company under TEP-3600;

Polyol-B: Polyether polyol with a number average molecular weight of 4,000, a functionality of 2, a hydroxyl value of about 28 mg KOH/g, obtained from Tianjin Petrochemical Company under TED-28;

Polyol-C: Styrene-acrylonitrile copolymerization grafted polyether polyol with a solid content of about 45% and a hydroxyl value of about 21 mg KOH/g, obtained from Zibo Dexin Lianbang Chemical Industry Co., Ltd. under POP-H45;

1 ,4-butanediol (1 ,4-BDO): chain extender;

Distilled water (H20): foaming agent;

Catalyst A: amine gel-type catalyst, Dabco S 25B from Air product;

Foam stabilizer: Niax L5302 from WITCO Chemical Co.,

Isocyanate prepolymer component (NCO% = 20%) , obtained by reaction of diphenylme- thane-4, 4'-diisocyanate and carbodiimide-modified diphenylmethane-4,4'-diisocyanate with pol- yether polyols having 13wt% EO (blocked) and a number average molecular weight of about 4,800 and a functionality of 3; available from BASF Polyurethane (China) Co., Ltd. under Elas- topan CS9500 C-B.

The E-TPU particles are oval particles with a diameter of about 4-5 mm and a density of 210 kg/m ³ , trade name Infinergy™ obtained from BASF Polyurethanes Specialty Products Co., Ltd.

Comparative example

The polyol component in Table 1 below was premixed with chain extender (1 ,4-BDO), cata- lyst (Dabco S 25B), foaming agent (distilled water), foam stabilizer (Niax L5302) to obtain pre- mixed polyol composition (453.3 g). The isocyanate prepolymer component (346.7 g) and the premixed polyol composition were respectively added into the corresponding charging barrel of a low-pressure casting machine and preheated to 40°C respectively. Steel mold with a centri- fuge was opened and set at 50°C. The isocyanate prepolymer component and the premixed polyol composition were poured into a rotating mold through stirring head of the low-pressure casting machine (N-type two-component pouring machine of Taiwan Green Industries Co., Ltd.). After aging for 4 minutes, the mold was opened to obtain the molded tire.

Example 1

E-TPU particles (73.6 g) were preliminarily put into the mold, then the mold was closed and the centrifuge was turned on to rotate the mold. The temperature of the mold was set at 50°C. The polyol component in Table 1 below was premixed with chain extender (1 ,4-BDO), catalyst (Dabco S 25B), foaming agent (distilled water), foam stabilizer (Niax L5302) to obtain premixed polyol composition (372.1 g). The isocyanate prepolymer component (290.6g) and the premixed polyol composition were respectively added into the corresponding charging barrel of a low- pressure casting machine and preheated to 40°C respectively. The isocyanate prepolymer component and the premixed polyol composition were poured into a rotating mold through stir- ring head of the low-pressure casting machine (N-type two-component pouring machine of Tai- wan Green Industries Co., Ltd.). After aging for 4 minutes, the mold was opened to obtain the molded tire.

Example 2

E-TPU particles (128 g) were preliminarily put into the mold, then the mold was closed and the centrifuge was turned on to rotate the mold. The temperature of the mold was set at 50°C. The polyol component in Table 1 below was premixed with chain extender (1 ,4-BDO), catalyst (Dabco S 25B), foaming agent (distilled water), foam stabilizer (Niax L5302) to obtain premixed polyol composition (285.2g). The isocyanate prepolymer component (226.8g) and the premixed polyol composition were added into the corresponding charging barrel of a low-pressure casting machine and preheated to 40°C respectively. The isocyanate prepolymer component and the premixed polyol composition were poured into a rotating mold through stirring head of the low- pressure casting machine (N-type two-component pouring machine of Taiwan Green Industries Co., Ltd.). After aging for 4 minutes, the mold was opened to obtain the molded tire.

The sheets for testing the physical properties were prepared by respectively injecting the corresponding isocyanate prepolymer component and the premixed polyol composition of the above Comparative Examples and Examples into a test piece mold of 20 cm ^* 15 cm ^* 1 cm under the corresponding test conditions. In preparing the test pieces of Example 1 and Example 2, the corresponding weight proportions of E-TPU particles were preliminarily put in a mold and then the corresponding isocyanate prepolymer component and premixed polyol composition were injected.

Example 3

E-TPU particles (53.6 g) were preliminarily put into the textured tire mold, then the mold was closed and the centrifuge was turned on to rotate the mold. Non-expanded elastomeric polyurethane composition (320 g) (Elastopan CS7579/128 C-A & Elastopan CS9500 C-B from BASF Polyurethane (China) Co., Ltd.) was firstly injected to cover the pattern area completely and then waited for 40 seconds. The outer tire was in a semi-cured state and the mold was al- lowed to continue to rotate. The corresponding isocyanate prepolymer component (211.3) and premixed polyol composition (271 g) of Example 1 was then poured into the mold. Double- density integrated tire was taken out after aging for 4 minutes.

Table 1

Note: the premixed polyol composition includes polyols, 1 ,4-BDO, Dabco S 25B, Niax L5302, and distilled water.

Table 2 : The physical properties of the tires obtained according to the Comparative exam- pies and Examples.

Thus , it can be seen that the tires produced by the method of the present invention have low density, light weight and good rebound resilience, while other physical properties remain comparable and even better.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. Thus, it is intended that the present invention cover such modifications and variations as come within the scope of the appended claims and their equivalents.