Fiber reinforced tape

Abstract

The invention relates to a fiber-reinforced tape comprising a thermoplastic composition comprising a propylene-based polymer and a plurality of continuous glass fibers dispersed in the thermoplastic composition, wherein each of the plurality of continuous glass fibers extends in the longitudinal direction of the tape, wherein the thermoplastic composition has a crystallization temperature determined by differential scanning calorimetry according to ISO 11357-3 using a heating rate of 10˚C / min and a cooling rate of 10˚C / min of at least 122.0 ⁰C.

Description

23POLYO 2-WO-ORD 1FIBER REINFORCED TAPEThe present invention relates to a fiber reinforced tape and a process for producing such tape. The present invention further relates to a laminate made from such tape and an article comprising such tape or such laminate.A fiber reinforced thermoplastic polymer composition in which a thermoplastic polymer is reinforced by glass fibers is widely used. The glass fibers may be chopped before being melt-mixed with the thermoplastic polymer to be dispersed therein. Alternatively, the glass fibers may be combined with the thermoplastic polymer as long glass fibers without chopping.WO2016142786A1 discloses a method for producing a fiber-reinforced composite tape, the method comprising: supplying a sheet or film of a matrix material between first and second spreaded fiber layers, each having a plurality of fibers; heating the sheet or film of the matrix material; pressing the first and second spreaded fiber layers into the matrix material; and cooling the matrix material. An apparatus for performing the method is also disclosed. A laminate comprising the tapes is also disclosed.Important mechanical properties of tapes and laminates made therefrom include strain at break and crack density growth rate.It is an objective of the present invention to provide a fiber reinforced tape having a high strain at break and low crack density growth rate.Accordingly, the present invention provides a fiber-reinforced tape comprising a thermoplastic composition comprising a propylene-based polymer and a plurality of continuous glass fibers dispersed in the thermoplastic composition, wherein each of the plurality of continuous glass fibers extends in the longitudinal direction of the tape, wherein the thermoplastic composition has a crystallization temperature determined by differential scanning calorimetry according to ISO 11357-3 using a heating rate of 10°C / min and a cooling rate of 10°C / min of at least 122.0 °C.According to the invention, a fiber reinforced tape having a high strain at break and low crack density growth rate was surprisingly obtained.23POLYO 2-WO-ORD 2The thermoplastic composition comprises a propylene-based polymer. The thermoplastic composition may further comprise a nucleating agent and / or additives.Preferably, the propylene-based polymer is a propylene homopolymer or a propylene copolymer with at most 10 wt% of comonomer units. The comonomer units may be ethylene monomer units and / or an a-olefin monomer units having 4 to 10 carbon atoms. For example, the propylene-based polymer may be a random propyleneethylene copolymer consisting of 90 to 99 wt% of propylene monomer units and 1 to 10 wt% of ethylene monomer units.Preferably, the propylene-based polymer is a propylene homopolymer.Preferably, the propylene-based polymer has a melt flow index determined according to ISO1133-1 :2022 at 230 °C and 2.16 kg of 100 to 120 g / 10min, more preferably 110 to 115 g / 10min.Preferably, the propylene-based polymer has Mw of 115 to 125 kDa, more preferably 117 to 122 kDa.Preferably, the propylene-based polymer has Mw / Mn of 2.5 to 7.0, more preferably 2.6 to 6.0, more preferably 2.7 to 5.5, more preferably 2.8 to 5.0, more preferably 2.9 to 4.0, more preferably 3.0 to 3.5.Mw and Mn are determined by ASTM D6474-12, preferably according to the method described in the experimental section of the present disclosure.Preferably, the propylene-based polymer has been prepared using a Ziegler-Natta catalyst.Preferably, the amount of propylene-based polymer in the thermoplastic composition is at least 90 wt%, more preferably at least 95 wt% with respect to the total thermoplastic composition.Nucleating agent23POLYO 2-WO-ORD 3Preferably, the thermoplastic composition further comprises a nucleating agent. The presence of a nucleating agent in the composition according to the invention leads to an increase in the crystallization temperature of the thermoplastic composition.For purpose of the invention with nucleating agent is meant any material that effectively accelerates the phase change from liquid polymer to semi-crystalline polymer (evident via faster crystallization rates measured with a differential scanning calorimeter or small crystallites observed with an optical microscope).Preferably, the nucleating agent comprises a cyclic dicarboxylate salt compound, preferably a cyclic dicarboxylate metal salt.Cyclic dicarboxylate metal salts suitable for use as the nucleating agent include those salts described in U.S. Pat. Nos. 6,465,551 and 6,534,574. The cyclic salts have the structure shown below:wherein Mi and M2are independently selected from the group consisting of: sodium, calcium, strontium, lithium, zinc, magnesium, and monobasic aluminum; wherein Ri, R2, RS, R4, R5, Re, R7, Rs, R9, and R10 are independently selected from the group consisting of: hydrogen and C1 -C9 alkyls; and further wherein any two adjacently positioned R3-R10 alkyl groups optionally may be combined to form a carbocyclic ring.In particular, suitable cyclic dicarboxylate metal salts include disodium bicyclo[2.2.1 ]heptane-2,3- dicarboxylate, calcium bicyclo[2.2.1]heptane-2,3- dicarboxylate, and combinations thereof. One may employ HYPERFORM® HPN-68 or HPN-68L from Milliken & Company of Spartanburg, South Carolina. HPN-68L is commercially sold, and comprises the disodium bicyclo [2.2.1 ] heptane-2, 3- dicarboxylate, as shown below:23POLYO 2-WO-ORD 4Other suitable cyclic dicarboxylate metal salts include metal salts of hexahydrophthalic acid (HHPA) having a structure as shown below:wherein Mi and M2 are the same or different, and may be combined into one cation, and are selected from at least one metal cation of calcium, strontium, lithium, and monobasic aluminum; and wherein Ri, R2, R3, R4, R5, Re, R7, Rs, R9, and R10 are either the same or different and are individually selected from the group consisting of hydrogen, C1- C9 alkyl, hydroxy, C1-C9 alkoxy, C1-C9 alkyleneoxy, amine, and C1-C9 alkylamine, halogens, and phenyl. In one preferred embodiment, the M1 and M2 are combined as a calcium ion.In particularly preferred embodiments, the nucleating agent comprises a cyclic dicarboxylate salt compound having the structure shown below:23POLYO 2-WO-ORD 5Hyperform® HPN-20E™ commercialized by Milliken comprises such a calcium cishexahydrophthalate compound of Formula (I) as nucleating agent and a stearate- containing compound as acid scavenger, e.g. zinc stearate.Preferably, the nucleating agent comprises a cyclic dicarboxylate salt compound and talc. In particularly preferred embodiments, the nucleating agent comprises a first nucleating agent which comprises a cyclic dicarboxylate salt compound; and a second nucleating agent which comprises talc, wherein the cyclic dicarboxylate salt compound has the formula (I):The weight ratio between the cyclic dicarboxylate salt compound and talc may be in a weight ratio of from 1 :1200 to 2:1 ; preferably in a ratio of from 1 :500 to 1 :1 ; more preferably in a ratio of from 1 :100 to 1 :2; even more preferably in a ratio of from 1 :50 to 1 :5. Such nucleating compositions are as described in W02014202603 and WO2014202604.Preferably, the amount of the nucleating agent in the thermoplastic composition is 0.01 to 0.50 wt%, more preferably 0.02 to 0.30 wt%, more preferably 0.03 to 0.10 wt%, with respect to the total thermoplastic composition.Preferably, the amount of the calcium cis-hexahydrophthalate compound of Formula (I) in the thermoplastic composition is 0.01 to 0.50 wt%, more preferably 0.02 to 0.30 wt%, more preferably 0.03 to 0.10 wt%, with respect to the total thermoplastic composition.AdditivesThe thermoplastic composition may further comprise one or more optional additives. Examples of suitable additives include a coupling agent to promote adhesion between a matrix material and fibers, an antioxidant, a heat stabilizer, a flow modifier, a flame retardant, a UV stabilizer, a UV absorber, an impact modifier, a cross-linking agent, a colorant and combinations thereof.23POLYO 2-WO-ORD 6Suitable examples of the coupling agent include a functionalized polyolefin grafted with an acid or acid anhydride functional group. The polyolefin is preferably polyethylene or polypropylene, more preferably polypropylene. The polypropylene may be a propylene homopolymer or a propylene copolymer. The propylene copolymer may be a propylene-a-olefin copolymer consisting of at least 70 wt% of propylene and up to 30 wt% of a-olefin, for example ethylene, for example consisting of at least 80 wt% of propylene and up to 20 wt% of a-olefin, for example consisting of at least 90 wt% of propylene and up to 10 wt% of a-olefin, based on the total weight of the propylene- based matrix. Preferably, the a-olefin in the propylene- a-olefin copolymer is selected from the group of a-olefins having 2 or 4-10 carbon atoms and is preferably ethylene. Examples of the acid or acid anhydride functional groups include (meth)acrylic acid and maleic anhydride. A particularly suitable material is for example maleic acid functionalized propylene homopolymer (for example Exxelor PO 1020 supplied by ExxonMobil and Fine-Blend® CMG5701 supplied by Fine-Blend Compatibilizer Jiangsu Co., Ltd). In particular maleic acid functionalized propylene homopolymer with low odor and TVOC is preferred, an example being Fine-Blend® CMG5701.Preferably, the amount of the coupling agent is 0.1 to 5.0 wt%, more preferably 0.2 to 3.0 wt%, more preferably 0.3 to 1 .0 wt%, with respect to the total thermoplastic composition.Preferably, the total amount of the propylene-based polymer, the nucleating agent and the additives is 100 wt% with respect to the total thermoplastic composition.The thermoplastic composition has a crystallization temperature determined by DSC according to ISO 11357-3 using a heating rate of 10°C / min and a cooling rate of 10°C / min of at least 122.0 °C, for example 122.0 to 132.0 °C, preferably 124.0 to 130.0 °C.Preferably, the thermoplastic composition has a melt flow index determined according to ISO1133-1 :2022 at 230 °C and 2.16 kg of 100 to 120 g / 10min, more preferably 110 to 115 g / 10min.Preferably, the thermoplastic composition has Mw of 115 to 125 kDa, more preferably 117 to 122 kDa.23POLYO 2-WO-ORD 7Preferably, the thermoplastic composition has Mw / Mn of 2.5 to 7.0, more preferably 2.6 to 6.0, more preferably 2.7 to 5.5, more preferably 2.8 to 5.0, more preferably 2.9 to 4.0, more preferably 3.0 to 3.5.Continuous qlass fibersThe continuous glass fibers can have an average filament cross-sectional area of from 75 pm2to 460 pm2.In the fiber-reinforced tape according to the invention, the weight ratio between the thermoplastic composition and the plurality of continuous glass fibers is preferably 90: 10 to 60:40, more preferably 80: 10 to 65:35.ProcessThe invention further provides a process for preparing the tape according to the invention, comprising the sequential steps of: a) supplying a sheet of the thermoplastic composition between a first layer of a plurality of spreaded continuous glass fibers and a second layer of a plurality of continuous glass fibers; b) heating the sheet of the thermoplastic composition and c) pressing the first layer and the second layer into the thermoplastic composition; and d) cooling the thermoplastic composition.The process may be performed as described in WO2016142786A1 , incorporated herein by reference.In particular, the process may be performed by apparatuses described in

[0082] -

[0105] comprising a spreading section and an impregnating section.LaminateThe tape according to the invention may be made into a laminate. Thus, the invention provides a laminate of a plurality of tapes of the invention. Within the framework of the invention, with' laminate’ is meant an arrangement in which at least two plies (layers) of the tapes of the invention are present, this can be understood as the laminate comprises at least two tapes. For example, such laminate contains 2, 3, 4, 5, 6, 7, 8, 9, 10, or more plies, wherein one ply consists of the tape of the invention.23POLYO 2-WO-ORD 8For example, in the laminate, the plies may be positioned such that their respective tape lengths are not parallel to each other. In case their respective tape lengths are positioned in relation to one other in a substantially 90° angle, such laminate is usually referred to as cross-ply. Laminates of the invention can for example be assembled or processed into two-dimensional or three-dimensional structures, such as, for example, via winding and / or lay-up techniques. In another aspect, the invention relates to an article comprising the tape of the invention or the consolidated laminate of the invention.ArticleThe invention provides an article comprising the tape according to the invention or the laminate according to the invention. The article may be selected from automotive exterior parts like bumpers and tailgates, automotive interior parts like instrument panels, automotive parts under the bonnet. The article may be also be selected from parts and housings of air conditioners, dishwashers, washing machines, dryers, coffee machines, power tools (e.g. saws, drills), durable goods (e.g. furniture), 5G antennas, solar panels, bikes and steps. The article may be electric vehicle battery housing or electric vehicle battery tray. The article may be scaffolding or construction frames or flooring.It is noted that the invention relates to the subject-matter defined in the independent claims alone or in combination with any possible combinations of features described herein, preferred in particular are those combinations of features that are present in the claims. It will therefore be appreciated that all combinations of features relating to the composition according to the invention; all combinations of features relating to the process according to the invention and all combinations of features relating to the composition according to the invention and features relating to the process according to the invention are described herein.It is further noted that the term ‘comprising’ does not exclude the presence of other elements. However, it is also to be understood that a description on a product / composition comprising certain components also discloses a product / composition consisting of these components. The product / composition consisting of these components may be advantageous in that it offers a simpler, more economical process for the preparation of the product / composition. Similarly, it is also to be understood that a description on a process comprising certain steps also discloses a process consisting of these steps. The process consisting of these steps23POLYO 2-WO-ORD 9 may be advantageous in that it offers a simpler, more economical process.When values are mentioned for a lower limit and an upper limit for a parameter, ranges made by the combinations of the values of the lower limit and the values of the upper limit are also understood to be disclosed.The invention is now elucidated by way of the following examples, without however being limited thereto.Polypropylene compositions shown in Table 1 were provided. The polypropylene compositions of Table 1 were used for preparing tapes having a thickness of 0.25 mm. The method for preparing the tapes as follows and was according to the method described in WO2016142786A1 :Bundles of glass fibers were introduced into a unidirectional tape production line. Glass fibers from the fiber bundles were continuously pulled through the production line by a pulling station located at the end of the production line. The fibers were separated into two groups, one of which was processed by the lower section of a spreading unit to produce a lower spreaded fiber layer and the other of which was processed by the upper section of the spreading unit to produce an upper spreaded fiber layer.Maleic anhydride grafted polypropylene and an antioxidant package were added to the polypropylene compositions of Table 1 to obtain compositions for preparing tapes (“tape polymer composition”). Number average molecular weight Mn and weight average molecular weight Mn of the tape compositions were measured and are shown in Table 2.The tape polymer composition (matrix material) was brought into contact with the top surface of the lower spreaded fiber layer. The upper and lower spreaded fiber layers were combined and pressed into the matrix material by passing over a series of pins. The combined spreaded fiber layers were consolidated into a unidirectional tape. The amount of the glass fibers in the tape was 70 wt% with respect to the tape.Transverse and cross ply laminates were produced from these tapes. Transverse laminates were made with a

[0090] 4slayup in stacks of 8 layers of the tapes.Cross-ply laminates were produced with a [02 / 90]slayup in stacks of 6 layers of the tapes.23POLYO 2-WO-ORD 10Prior to creating the stacks, tapes were cut to appropriate length at an angle of 90° with the glass fibers. Upon making the stack, the upper half of the sheets was turned upside down to retain a symmetrical laminate. Laminates were then compression molded using a Fontijne LabPro press with attached cassette cooling system. The stacks were placed between glossy stainless steel plates to ensure a smooth surface. Furthermore, the mold was cleaned and coated with the release agent Marbocote 227-CEE before the sheets were stacked. The pressure was set to 2 bar (a force of 12.5 kN) during the compression molding, which was carried out in a positive mold to allow to keep pressure on the stack during the entire molding process. The stack was first heated to a temperature of 220°C with a heating rate of 20°C / min. This temperature was retained for 15 minutes after which the stack was cooled down with a rate of 10°C / min. The molding process was finished when a temperature of 25°C was reached. In this way laminates with a dimension of 250x250 mm were made.Tensile specimens were sawn from the laminates using a table circular saw with diamond blade and water cooling. First, the outer 2 cm were sawn off from the stack to remove possible irregularities in the vicinity of the edge. Thereafter, tensile specimens were sawn in the desired direction. The tensile bar dimensions are based on ASTM D3039 / D3039M, however, the width was reduced to 20 mm to match the width of the clamps. The dimensions of the test specimens were 175x20 mm (length x width). After sawing, the specimens were deburred.Properties of the transverse laminate and properties of the cross-ply laminate were measured using these tensile specimens and the results are shown in Table 3.Table 1 : polypropylene compositions23POLYO 2-WO-ORD 11Table 2: tape polymer compositionsTable 3: laminatesIt can be understood that the laminate according to the invention has a higher average fracture strain.It can further be understood that the laminate according to the invention has lower crack densities at the same strain and the development of the cracks is slower.MFIMelt flow index was determined according to ISO1133-1 :2022 at 230 °C and 2.16 kg.Crystallization temperatureCrystallization temperature of the polypropylene composition was determined by differential scanning calorimetry (DSC) according to ISO 11357-3 using a heating rate of 10°C / min and a cooling rate of 10°C / min by the following method:First, samples are heated to 220°C with a rate of 10°C / min. This temperature is maintained for 15 minutes. Subsequently, the sample is cooled down to 25°C with a rate of 10°C / min. This temperature is kept for 5 minutes. Lastly, the sample is heated with a rate of 10°C / min to record the second heating curve following from the aforementioned crystallization conditions.23POLYO 2-WO-ORD 12Mw, MnMw and Mn were all measured in accordance with ASTM D6474-12 (Standard Test Method for Determining Molecular Weight Distribution and Molecular Weight Averages of Polyolefins by High Temperature Gel Permeation Chromatography). Mw stands for the weight average molecular weight and Mn stands for the number average weight. In addition to the method specified by ASTM D6474-12, the method was performed using a configuration in which a Polymer Char IR5 infrared concentration detector and a Polymer Char online viscosity detector was used to gain ‘absolute’ or accurate molar masses. Three columns of Polymer Laboratories 13 pm PLgel Olexis, 300 x 7.5 mm were used in series with 1 ,2,4-trichlorobenzene stabilized with 1 g / L butyl hydroxytoluene (also known as 2,6-di-tert-butyl-4-methylphenol or BHT) as eluens. The molar mass was determined based on a calibration using linear PE standards (narrow and broad (Mw / Mn = 4 to 15)) in the range of 0.5 - 2800 kg / mol . Samples of polymer granules were mixed with Tris (2,4-di-tert-butylphenyl)phosphite (Irgafos 168) and 1 ,1 ,3-Tris (2-methyl-4-hydroxy-5-tert-butylphenyl)butane (Topanol CA) in a weight ratio sample : Irgafos : Topanol of 1 :1 :1 , after which the mixture thus obtained was dissolved in 1 ,2,4-trichlorobenzene stabilized with 1 g / L BHT until the concentration of the mixture in 1 ,2,3-trichlorobenzene stabilized with 1 g / L BHT was 0.03 wt%.Transverse ply: fracture strainTo determine the fracture strain of transverse-ply laminates, transverse-ply specimens were tested using a Zwick Retroline 1445 with a 50 kN load cell, equipped with a Zwick dual clip-on extensometer with a gage length of 25 mm, was used. To determine the matrix fracture strain, measurements were carried out in triplo on the transverse ply specimens. All measurements were performed with a strain rate of 10'5s-1at a temperature of 21 °C.Cross-ply laminate: crack densityTo determine the transverse crack density in cross-ply laminates, cross-ply specimens were tested using the Zwick Retroline 1445 with 50kN load cell. A grip length to 40 mm with a grip-to-grip separation of 95 mm is used. Prior to the measurements, one side of each specimen was polished with a Struers handpolisher so that cracks become visible under the Keyence VHX 7000 digital microscope (magnification 400x).Multiple tensile tests were performed on each type of specimen, and aborted at increasing strain levels. The strain levels at which tests were aborted were chosen to23POLYO 2-WO-ORD 13 increase with steps of 0.2% per measurement, until a maximum strain of 3% is reached. All measurements are performed at a strain rate of 10-4s-1and a temperature of 21°C, and carried out at least in duplo. The samples were observed with microscope to determine the number of cracks. The crack density was calculated by dividing the number of cracks by the total length of the area considered.

Claims

23POLYO 2-WO-ORD 14CLAIMS1 . A fiber-reinforced tape comprising a thermoplastic composition comprising a propylene-based polymer and a plurality of continuous glass fibers dispersed in the thermoplastic composition, wherein each of the plurality of continuous glass fibers extends in the longitudinal direction of the tape, wherein the thermoplastic composition has a crystallization temperature determined by differential scanning calorimetry according to ISO 11357-3 using a heating rate of 10°C / min and a cooling rate of 10°C / min of at least 122.0 °C.

2. The fiber-reinforced tape according to claim 1 , wherein the thermoplastic composition further comprises a nucleating agent, preferably wherein the amount of the nucleating agent in the thermoplastic composition is 0.01 to 0.50 wt%, more preferably 0.02 to 0.30 wt%, more preferably 0.03 to 0.10 wt%, with respect to the total thermoplastic composition.

3. The fiber-reinforced tape according to claim 2, wherein the nucleating agent comprises a cyclic dicarboxylate salt compound.

4. The fiber-reinforced tape according to any one of the preceding claims, wherein the thermoplastic composition further comprises a coupling agent, preferably wherein the amount of the coupling agent is 0.1 to 5.0 wt%, more preferably 0.2 to 3.0 wt%, more preferably 0.3 to 1 .0 wt%, with respect to the total thermoplastic composition.

5. The fiber-reinforced tape according to claim 4, wherein the coupling agent comprises a functionalized polyolefin grafted with an acid or acid anhydride functional group.

6. The fiber-reinforced tape according to any one of the preceding claims, wherein the propylene-based polymer has a melt flow index determined according to ISO1133- 1 :2022 at 230 °C and 2.16 kg of 100 to 120 g / 10min, more preferably 110 to 115 g / 10min.

7. The fiber-reinforced tape according to any one of the preceding claims, wherein the propylene-based polymer has Mw of 115 to 125 kDa, more preferably 117 to 122 kDa and / or Mw / Mn of 2.5 to 7.0, more preferably 2.6 to 6.0, more preferably 2.7 to23POLYO 2-WO-ORD 155.5, more preferably 2.8 to 5.0, more preferably 2.9 to 4.0, more preferably 3.0 to3.5, wherein Mw and Mn are determined by ASTM D6474-12.

8. The fiber-reinforced tape according to any one of the preceding claims, wherein the propylene-based polymer is a propylene homopolymer or a propylene copolymer with at most 10 wt% of comonomer units.

9. The fiber-reinforced tape according to any one of the preceding claims, wherein the propylene-based polymer has been prepared using a Ziegler-Natta catalyst.

10. The fiber-reinforced tape according to any one of the preceding claims, wherein the crystallization temperature of the thermoplastic composition is 122.0 to 132.0 °C, preferably 124.0 to 130.0 °C .

11. The fiber-reinforced tape according to any one of the preceding claims, wherein the amount of propylene-based polymer in the thermoplastic composition is at least 90 wt%, more preferably at least 95 wt% with respect to the total thermoplastic composition.

12. The fiber-reinforced tape according to any one of the preceding claims, wherein the weight ratio between the thermoplastic composition and the plurality of continuous glass fibers is 90: 10 to 60:40, preferably 80: 10 to 65:35.

13. A process for preparing the tape according to any one of claims 1-12, comprising the sequential steps of: a) supplying a sheet of the thermoplastic composition between a first layer of a plurality of spreaded continuous inorganic fibers and a second layer of a plurality of spreaded continuous inorganic fibers; b) heating the sheet of the thermoplastic composition and c) pressing the first layer and the second layer into the thermoplastic composition; and d) cooling the thermoplastic composition.

14. A laminate of a plurality of the tapes according to any one of claims 1-12, wherein the laminate comprises at least two tapes, wherein the laminate is a cross-ply.23POLYO 2-WO-ORD 1615. An article comprising the tape according to any one of claims 1-12 or the laminate according to claim 14, wherein the article is selected from the group consisting of automotive exterior parts like bumpers and tailgates; automotive interior parts like instrument panels; automotive parts under the bonnet; electric vehicle battery housing; electric vehicle battery tray; scaffolding; construction frames and flooring; parts and housings of air conditioners; dishwashers; washing machines; dryers; coffee machines; power tools (e.g. saws, drills); durable goods (e.g. furniture); 5G antennas; solar panels; bikes and steps.

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