CN117183514A - High resilience film with multi-layer structure and preparation method thereof - Google Patents

Abstract

The invention discloses an elastic membrane with an ABA three-layer structure and a preparation method thereof, wherein a core layer of the elastic membrane comprises an SBC material, a surface layer of the elastic membrane comprises a low-modulus PE serving as a main body, and EVA, TPEE or POE is used for blending modification; the total thickness of the single surface layer is 1-5 mu m, which accounts for 2-10% of the total thickness of the whole elastic film, and the two surface layers account for 4-15% of the total thickness of the whole elastic film. The elastic film has a permanent deformation rate of 12% or less and an elongation at break of 500% or more. The surface layer of the elastic film can provide an anti-sticking effect, has soft hand feeling, reduces the constraint of the surface layer to the elastic layer to the minimum, does not need pretreatment when in use, and can be widely applied to products such as trousers waistbands, cuff elastic bands, paper diaper elastic waistlines and the like in clothing industry and sanitary material industry. The elastic fabric has good elasticity and softness, so that a comfortable fitting feel can be brought to a wearer.

Description

High resilience film with multi-layer structure and preparation method thereof

Technical field

The present invention relates to a high resilience film with a multi-layer structure and a preparation method thereof. More specifically, the present invention relates to an elastic film with a soft surface layer that does not require pretreatment and a preparation method thereof.

Background technique

The characteristic of elastic film products is that they have a high rebound rate. They generally use single elastomers such as TPU, EVA, TPEE, POE, SIS, SBS, SEBS, SEPS, etc. or their mixtures as the main raw materials. However, because this type of elastomer generally has high viscosity, when it is processed into a film, the films will stick to each other and become unusable.

In the existing technology, the industry generally adopts two types of technical solutions to solve such problems. The first type of technical solution is to add calcium carbonate, silica, erucamide, oleic acid amide, silicone, etc. as opening agents. This type of opening agent reduces the contact between films by forming a lubricating layer or micro-protrusions on the film surface. Thereby reducing the stickiness between films. However, in order to achieve the ideal opening effect of this type of opening agent, it usually needs to be added in a higher proportion. This will not only weaken the rebound of the film, but also lead to a series of problems such as poor subsequent compounding; the second type of technical solution is to use shower A layer of non-sticky polymer layer is laminated or co-extruded so that the core elastic layer is wrapped to solve the sticking problem. When using the cladding process, the composite layer needs to be torn apart and discarded. This process is troublesome and will also cause waste of the cladding layer. When using the co-extrusion process, there is no need to peel off the surface layer during use.

United States Patent Application US 2003/0181120 A1 discloses a breathable, progressively stretchable elastic composite material comprising an inner elastic film and an outer nonwoven web extrusion laminated to each surface of the film. The internal elastic film has large pores formed by random incremental stretching and essentially no pore-forming filler. In one embodiment, the elastic composite material includes an elastic film and a nonwoven web extrusion laminated to one or both surfaces of the film. Fabrication methods for elastic composites include extrusion lamination and incremental stretching, and can be used to form garments and disposable items.

US Patent No. 7,879,452 B2 discloses a non-block multilayer film, including a first brittle polymer film layer and a second elastic polymer film layer, wherein the first brittle polymer film layer cannot be stretched beyond the original size. 110% without breaking, the first brittle polymer film layer can be connected to the second elastomeric film layer by co-extrusion, extrusion coating, adhesive bonding, thermal bonding, ultrasonic bonding, calendering bonding, point bonding, etc. a first surface of the polymer film layer; the multilayer film can be activated by tensile fracture of the first brittle polymer film layer to stretch to at least 150% of its original size and recover no more than 120% of its original size; The brittle polymer may be selected from polystyrene, acrylate polymers, polycarbonate and combinations thereof, especially polystyrene, and the elastomeric polymer may be selected from block copolymers of vinyl aromatics and conjugated diene monomers, Natural rubber, polyurethane rubber, polyester rubber, elastomeric polyolefins, elastomeric polyamides and mixtures thereof.

U.S. Patent No. 9,669,606 B2 discloses an elastic film, which may include a first layer composed of: (i) at least 50% of the elastic film at least one non-styrene elastic polymer selected from polypropylene and Copolymers of polyethylene and mixtures thereof; and (ii) at least one draw down polymer accounting for 5% to 25% of the layer selected from linear low density polyethylene, high density polyethylene, polyethylene Propylene homopolymers and mixtures thereof; elastic films having a basis weight not exceeding about 25 gsm and a permanent deformation not exceeding about 14% after initial stretching to twice the original size. The elastic film of this patent may also include a second layer consisting of: (a) at least one elastomeric polymer, (b) a second pull-down polymer, where the basis weight of the elastic film does not exceed 40 gsm, double stretch The final permanent deformation rate does not exceed approximately 14%. Wherein, the elastomeric polymer of the second layer may be a non-olefin-based elastomeric polymer, such as a block copolymer of vinyl aromatic hydrocarbons and conjugated dienes, natural rubber, polyester rubber, polyamide Elastomers, polyether elastomers, polyisoprene, polychloroprene and mixtures thereof, in particular styrene block copolymers, such as styrene-butadiene-styrene block copolymers, styrene- Isoprene-styrene block copolymer, styrene-isoprene-butadiene-styrene block copolymer, styrene-ethylbutylene-styrene block copolymer, styrene-ethylene - Propylene block copolymer, styrene-ethylene-propylene-styrene block copolymer, styrene-ethylene-ethylene-propylene-styrene block copolymer and mixtures thereof, the second pull-down polymer may be selected from polystyrene Ethylene, high impact polystyrene, linear low density polyethylene, high density polyethylene, high density polyethylene, polypropylene homopolymers and mixtures thereof.

U.S. patent US10,239,295B2 (the same family includes Chinese patent 201680009617.7, announcement number CN107454870 B) discloses a split-layer thermoplastic film, which has the structure A-(B-C)n-B-A, where n≥1, A and C each have a thickness and Each independently includes an inelastic layer of at least one of polymer compositions A and C; B is an elastic layer containing polymer composition B, wherein: a) the layers containing (B-C)n-B have a combined thickness x; b) Polymer compositions A and C include inelastic polymers; c) Polymer composition B includes elastomeric polymers; d) The thickness of C accounts for less than or equal to 5% of the total film thickness; wherein the film has a notch el The Mendorf tear strength is at least 2 times the notched Elmendorf tear strength of the comparative thermoplastic film having structure A-B-A, A and B including substantially the same polymer compositions A and B as the thermoplastic film, and wherein The thickness y of the B-layer in the comparative thermoplastic film is essentially equal to x. Among them, the inelastic polymer is selected from polyolefins, styrenic polymers, acrylic polymers, polyamides and mixtures thereof, and the polyolefin is selected from polyethylene, polypropylene, linear low-density polyethylene, low-density polyethylene, High-density polyethylene, its homopolymers, its copolymers and mixtures thereof; the elastomeric polymer is selected from the group consisting of styrene-based block copolymers, elastomeric olefin block copolymers or mixtures thereof, and the styrene-based block copolymer is selected from From styrene-butadiene-styrene, styrene-isoprene-styrene, styrene-ethylbutylene-styrene, styrene-ethylene-propylene, styrene-ethylene-propylene-styrene, Styrene-ethylene-ethylene-propylene-styrene, polystyrene, high-impact polystyrene and mixtures thereof.

Chinese invention patent 201880022360.8 discloses a structure used as clothing, protective gear, socks or shoes, which includes a low-resilience component 1 composed of a thermoplastic elastomer (X) and a high-resilience component composed of a thermoplastic elastomer (Y). The resilient member 2, the thermoplastic elastomer (X) and the thermoplastic elastomer (Y) are each independently formed from a resin composition containing the following components: (a) 100 parts of a hydrogenated block copolymer, which is composed of at least 2 The block copolymer formed by polymer block A and at least one polymer block B is hydrogenated, and 50 to 100% has a weight average molecular weight of less than 200,000. Polymer block A is derived from vinyl aromatic The structural unit of the compound is formed, and the polymer block B is formed from the structural unit derived from the conjugated diene compound; (b) 50 to 300 parts of hydrocarbon softener; and (c) relative to the total of (a) and (b) 100 parts is 3 to 50 parts of polyolefin resin. The hydrocarbon softener can be paraffin oil, naphthenic oil, aromatic oil, etc.; the polyolefin resin can be propylene polymer, ethylene polymer, or olefin copolymer. In this patent, the modulus of the thermoplastic elastomer (X) at 100% elongation is 1.0 MPa or less, and the hysteresis loss rate is more than 70%, and the modulus of the thermoplastic elastomer (Y) at 100% elongation is 1.0 MPa or less, and the hysteresis loss rate is less than 40%.

US patent application US 2021/0386904 A1 discloses a multi-layer thermoplastic film including an inner layer and two outer layers. The inner layer polymer composition includes: (a) 50%-95% selected from SBS, SIS, SIBS Non-hydrogenated styrene block copolymer, (b) olefin block copolymer. Among them, the outer layer includes polypropylene and polyethylene, the polypropylene accounts for at least 20% of the outer layer, and the thickness of each outer layer is 5%-15% of the total film thickness. The application's films are particularly suitable for use in fasteners, waistbands and cuffs for absorbent articles.

It can be seen that when forming an elastic film using a co-extrusion process, the existing technology usually uses LDPE and PP as surface materials. However, these materials have high hardness and no elasticity, making the finished product feel hard, have a strong plastic feel, and have a high permanent deformation rate. , the necking is severe when pre-tensioning is activated, and a special process is required to stretch and tear the surface layer before use to release the elasticity. The process is relatively complex.

Therefore, in view of the problems existing in the prior art, it is necessary to provide an elastic film prepared by a co-extrusion process, with an anti-sticking surface layer and good hand feel and low binding characteristics.

Contents of the invention

The object of the present invention is to provide an elastic film with a soft surface layer and no need for pretreatment, with an ABA three-layer structure and formed by three-layer co-extrusion.

In order to achieve the above-mentioned object of the invention, on the one hand, the present invention provides an elastic film with a soft surface layer and no need for pretreatment. The elastic film has an ABA three-layer structure; wherein, the core layer of the elastic film includes SBC materials, and the core layer The elastic layer is an elastic layer that provides elasticity to the elastic film; the surface layer of the elastic film includes low-modulus PE as the main body, such as PE with an elastic modulus less than 100 mpa, and is blended and modified with EVA, TPEE or POE, so that the surface layer has Soft feel; the thickness of each surface layer is 1-5μm, which accounts for 2% to 10% of the total thickness of the entire elastic film, and the thickness of the two surface layers accounts for 4% to 15% of the total thickness of the entire elastic film, making the surface layer The restraint of the elastic layer is reduced to a minimum, and no pretreatment is required during use; the permanent deformation rate of the elastic film is within 12%, preferably within 10%, the elongation at break is above 500%, preferably above 600%, and the stretch is 300% The necking is small, preferably less than 40%.

In the above-mentioned elastic film of the present invention, since the surface layer uses low-modulus PE and is blended and modified with EVA, TPEE or POE, the surface layer of the elastic film has a soft feel; and the thickness of the surface layer is controlled so that It accounts for a small proportion of the total thickness of the entire elastic membrane, and ensures that the surface layer of the elastic membrane minimizes the binding of the elastic layer, and does not require pre-treatment or pre-activation when used; at the same time, the surface layer will not stretch under normal stretching conditions. A fracture structure is formed, the permanent deformation rate of the entire elastic film is very small, and the elongation at break is high.

In the present invention, the term modulus refers to the ratio of stress to strain in a material under stress. Please note that the modulus can have different names corresponding to different stress states, such as tensile modulus (E), shear modulus (G), bulk modulus (K), longitudinal compression (L), etc. . The modulus in the present invention specifically refers to the elastic modulus, which refers to the proportional coefficient between stress and strain in the elastic deformation stage of the material (that is, in line with Hooke's law). Tensile elastic modulus E, also called Young's modulus.

In the present invention, the term permanent deformation rate refers to the percentage of the permanent deformation size of the material after the stress is removed to the original size. In practical standards, it generally refers to the deformation size of the material after the stress is removed and the material is parked for a certain period of time. Percentage of original size.

In the present invention, the term elongation at break refers to the ratio of the displacement value of the material when it is broken to its original length, expressed as a percentage.

In the present invention, the term necking refers to the phenomenon of local cross-sectional reduction that may occur in a material under tensile stress.

In the elastic film of the present invention, the SBC material in the core layer refers to a styrene block copolymer, preferably SIS, SBS, SEBS, SEPS and/or SEEPS, and more preferably SIS, SBS, SEBS or SEPS. Especially SEBS.

In the elastic film of the present invention, the core layer can be composed of SBC materials and elastomers. The elastomer can be EVA, TPEE, or POE, and its proportion in the core layer of the elastic film does not exceed 20wt%. Preferably no more than 10 wt%, more preferably no more than 5 wt%.

In the elastic film of the present invention, the low-modulus PE in the surface layer can be LLDPE, MLDPE, and/or ULDPE. These low-modulus PEs have a soft feel and high elongation at break.

In the elastic film of the present invention, the proportion of EVA, TPEE or POE in the surface layer is 5wt%-30wt%, preferably 10wt%-25wt%, and more preferably 15wt%-25wt%.

It is particularly important to note that the surface layer of the elastic film of the present invention does not contain rigid polymers such as PP.

As a specific embodiment of the present invention, the surface layer may further include 5 wt% to 15 wt% of an open masterbatch. The open masterbatch may be formed by adding inorganic powder to low modulus PE. For example, the opening masterbatch contains 2wt%-12wt% silica. More preferably, the opening masterbatch contains 3wt%-8wt% silica. The silica used can be silica with an average particle size of 2.5 μm. Silica powder.

In the present invention, the basis weight of the entire elastic film is preferably 20-80 gsm, more preferably 30-60 gsm; measured without applying pressure, the entire thickness is preferably 22-88 μm, more preferably 33-66 μm.

In addition, it should be noted that in the elastic membrane with an ABA three-layer structure of the present invention, the two surface layers are not necessarily the same in thickness, nor are they necessarily completely consistent in composition.

On the other hand, in order to achieve the object of the present invention, the present invention also provides the use of the above-mentioned elastic film in the preparation of clothing, surgical clothing or absorbent sanitary products.

In the present invention, the absorbent sanitary products may be diapers or other forms of products, especially disposable sanitary products. In the present invention, the term "disposable" means disposable after limited use without being cleaned or repaired for reuse.

The elastic film of the present invention has ultra-high resilience characteristics and is particularly suitable for preparing waistbands, cuff elastic bands or elastic waistbands for diapers.

On the other hand, in order to achieve the object of the present invention, the present invention also provides a method for preparing the above-mentioned elastic film. In this method, the ABA three-layer structure of the elastic film is formed using a true three-layer co-extrusion die structure. Wherein, the polymer or polymer mixture of each layer in the elastic film is melted separately, and the melted polymer is layered in the co-extrusion die and extruded from the die at the same time. Each co-extrusion There is no adhesive between the layers.

The traditional ABA structure co-extrusion process is realized by splitting the flow of the distributor. It is easy to cross-layer between the A layer and the B layer, resulting in unstable performance. However, after the present invention adopts the true three-layer die process, the thickness uniformity will be higher. Performance is more stable.

The elastic film with an ABA three-layer structure of the present invention has ultra-high resilience characteristics and can be widely used in the clothing industry and sanitary materials industry, such as trousers waistbands, cuff elastic bands, diaper elastic waistlines and other products. Because of its good elasticity and softness, it can provide the wearer with a comfortable fit.

Compared with the existing technology, the surface layer of the elastic film of the present invention is non-brittle. It uses low-modulus PE and is blended and modified with elastomer to give it a soft feel and an elongation at break of more than 500%. However, the surface layer of US 7,879,452 B2 uses a brittle polymer selected from polystyrene, acrylic polymer, polycarbonate and combinations thereof, and the elongation at break is less than 110%. US9,669,606B2, US 10,239,295 B2 and US 2021/ Polypropylene homopolymer is used in 0386904 A1, so the elastic film of the present invention recovers to within 110% after being stretched to 150%, with a lower permanent deformation rate and a better elastic recovery rate. The surface layer of the elastic film of the present invention can provide anti-sticking effect, and at the same time has the characteristics of good hand feeling and low binding.

Below, the present invention will be further described with reference to the drawings and specific embodiments. However, these specific embodiments are only illustrative of certain specific implementations of the present invention and are not intended to limit the present invention.

Description of the drawings

Figure 1 is the cross-sectional surface morphology of the elastic membrane prepared in Example 2 of the present invention;

Figure 2 is the cross-sectional surface morphology of the elastic membrane prepared in Comparative Example 5 of the present invention;

Detailed ways

Each polymer raw material used in the present invention is:

LLDPE is linear low density polyethylene LLDPE 7042 produced by Maoming Petrochemical

LDPE is low density polyethylene LDPE 0274 produced by Qatar Petrochemicals Co., Ltd.

POE is ENGAGE 8150, 8003, etc. produced by Dow Chemical Company

SIS produces D1114 for Caton Corporation of the United States

G1657 produced by SEBS for Caton Corporation of the United States

PP is HP 510 produced by CNOOC and Shell Petrochemical Co., Ltd.

The open masterbatch is configured by the applicant himself LLDPE 7042 + silica (Japanese Fuji Silicon Chemical SY530)

In the following examples and comparative examples, the test methods and test instruments for basis weight, permanent deformation rate, tensile strength, elongation at break, necking, thickness, etc. are as follows:

(1)Gram weight detection standard:

A) Testing instrument: analytical balance, accuracy 0.001g;

B) Sampling standards: starting from 15mm away from the edge in the width direction, sampling every 60mm, and sampling every 300mm in the long direction. The sample size is 100x100mm, and the number of sampling blocks is a total of 100 blocks in the direction of width and length in degrees Celsius;

(2)Permanent deformation rate:

A) Testing standards: company standards

B) Testing instrument: Tensile testing machine

C) Sampling standards:

C1. Wash your hands before testing to remove dust or oil that may affect the results;

C2. When samples are obtained from large batches (such as rolls of material), remove several layers of samples or boxes to ensure that the samples used for testing are free of contamination and damage;

C3. Use scissors to cut the sample from the roll. Material samples should be large enough to allow at least one 2.54 cm wide by 15.0 cm long sample to be cut in the desired orientation, either in the CD or MD direction for testing. If a sample average is desired, cut a sample large enough to allow the appropriate number of test specimens to be cut (each 2.54cm wide and 15.0cm long);

C4. Before cutting individual samples from each sample:

i. Make sure the sample is arranged in the desired test direction (CD or MD) before cutting;

ii. Ensure accurate cutting. The knife is sharp so the edges of the sample are cut without any defects or tears. Visually inspect the cut samples to check for any defects and discard any defective samples, especially at the edges;

C5. Using an accurate cutter, cut at least one 2.54cm wide and 15cm long sample in the desired direction (CD or MD) from the original sample. If the width of the sample is less than 2.54cm, use the width of the material as the sample width in the calculation. If the average value of the sample is desired, cut an appropriate number of test samples from the original sample. Avoid grabbing the area of the sample that will be tested (grab the ends of the sample that will be clamped);

C6. Adjust the sample state to 23℃±2℃ and relative humidity 50%±2%, and keep it for a minimum of two hours before testing;

D)Detection method:

Test steps:

D1. Test in an air-conditioned room at 23℃±2℃ and relative humidity of 50%±2%;

D2. Set the initial jaw air pressure based on the test material. A typical setting is 550kPa (approximately 80psi). If the sample slips, increase air pressure in the jaws;

D3. Insert one end of the sample into the upper jaw and close the jaw. Straighten the sample between stationary and moving jaws. Insert the other end of the sample into the lower jaw, using sufficient force to remove slack, but less than 0.05N of pretension to the load cell. After the sample is loaded, adjust the elongation indication and force indication of the tensile machine to zero;

D4. Adjust the clamp spacing length L0 to 50.8mm, check the jaws for accurate alignment and parallelism to ensure that the applied force does not cause angular deviation, set the constant elongation rate of the stretching machine to 254mm/min, and set the stretching The machine pre-tensions 0.1N;

D5. Start the stretching machine, stretch the sample to 200% elongation at the set speed, stop for one minute, and return to the initial position at the same speed;

D6. Repeat step 5 and read the sample length L1 under 0.1N pre-tension;

Results and representation:

Calculate the permanent deformation rate (%) according to the following formula

B is the permanent deformation rate,%

L ₀ is the initial clamp spacing length, in millimeters (mm)

L ₁ is the length of the sample when it returns to the zero position and rests for a predetermined time before applying pretension, in millimeters (mm)

(3) Tensile strength and elongation at break:

A) Testing standards: company standards

B) Testing instrument: Tensile testing machine

C) Sampling standards:

Same as the sampling standard for permanent deformation rate mentioned above

D)Detection method:

Test steps:

D1. Test in an air-conditioned room at 23℃±2℃ and relative humidity of 50%±2%;

D2. Set the initial jaw air pressure based on the test material. A typical setting is 550kPa (approximately 80psi). If the sample slips, increase air pressure in the jaws;

D3. Insert one end of the sample into the upper jaw and close the jaw. Straighten the sample between stationary and moving jaws. Insert the other end of the sample into the lower jaw, using sufficient force to remove slack, but less than 0.05N of pretension to the load cell. Do not zero the equipment after loading the sample;

D4. Turn on the tensile tester and data collection equipment at the same time according to the manufacturer's instructions;

D5. Observe the sample during testing to check for slippage. If slip is observed during testing, jaw air pressure should be gradually increased and a new sample retested until no slip is detected. The jaw pressure used is reported with the test results;

NOTE: Slippage of the specimen in the jaws will result in inaccurate values of elongation. To help confirm whether slippage has occurred, use a pen to mark the upper jaw contact jaw immediately after loading (do not mark the test area of the sample between the two jaws);

D6. Ensure that the instrument does not stop testing until the entire sample breaks. If the test is stopped early, or continues after the sample breaks, the break detector should be adjusted. This result should be discarded and another sample tested;

NOTE: If a specimen breaks at the flat clamp or bar line, this should be discarded and a new specimen tested. Data from this sample should not be used because the elongation and maximum strength data may not be accurate. If the sample consistently breaks at the jaw line, the air pressure is probably too high and should be reduced;

D7. Remove the sample from the jaws and return the cross-clamp of the equipment to the starting position to prepare for testing the next sample;

Calculation and reporting:

The basic output of the tensile tester is a force-elongation or force-strain curve; where:

Elongation at break % = (crosshead distance x 100)/clamp spacing

Breaking strength = peak maximum strength (N) (reported to the nearest 0.01N)

Tensile strength = breaking strength (N)/sample width (cm) (reported to the nearest 0.01N/cm)

(4) Neck:

A) Testing standards: company standards

B) Testing instrument: necking tester (this instrument has two clamps. The clamps are tightened by nuts. The clamps control the distance between the clamps by rotating the threaded rod. The distance between the clamps is displayed by a distance meter to display the real-time distance);

C) Sampling standards:

The same sampling standard for permanent deformation rate as mentioned above, except that the samples collected are at least 100mm wide and 200mm long;

D)Detection method:

Test steps:

D1. Test in an air-conditioned room at 23℃±2℃ and relative humidity of 50%±2%;

D2. Accurately cut samples with a width of 100mm and a length of 200mm;

D3. Adjust the distance between the clamps to 100mm, clamp the long end of the sample at both ends of the clamps, slightly tighten the film so that there is no slack, and tighten the clamps;

D4. Adjust the distance between the clamps to 300mm by rotating the threaded rod, and measure the width L of the sample in the middle of the two clamps at this time;

Calculation and results:

Neck rate (%) is calculated according to the following formula

In the formula, X is the necking rate, %

L is the width of the sample at the middle position when the clamp spacing is adjusted to 300mm, in millimeters/mm;

(5)Thickness:

A) Testing Standard: This method is technically the same as ASTM D645.

B) Testing instrument: scissors or knife: can cut the sample to the required size;

Thickness meter: reaches a sensitivity of 0.001mm;

C) Sampling standards:

- Allow the sample to equilibrate for 2 hours at 23°C (±2°C) and 50% relative humidity (±2%) before testing;

-Use scissors/knife to cut a strip from the sample that is larger than the size of the indenter contacting the sample;

- The test sample should be selected to be representative of the entire transverse direction of the sample.

D)Detection method:

Test steps:

D1. Prepare a micrometer with the designated anvil and weight;

D2. Before testing each sample, reset the thickness measuring instrument to zero;

D3. Before using the micrometer, ensure that the presser foot and anvil surfaces are clean, the instrument has been calibrated, and the instrument is installed on a solid horizontal surface without obvious vibration;

D4. When the presser foot is in the upward position, place the sample underneath. Use the handle to release the presser foot, which will slowly lower itself;

5. Record the measurement data after the preset delay time, accurate to 0.01mm, and for thin films, accurate to 0.001mm.

Calculation and reporting:

Report the mean and standard deviation to the nearest 0.01mm; for films <0.10mm: report to the nearest 0.001mm.

Configuration of open masterbatch

1. Accurately weigh 100 parts of resin and 5 parts of silica powder; 2. Pour into a mixer and mix for 30 minutes to fully mix evenly; 3. Put the mixed materials into a twin-screw extruder to melt Extrusion granulation; 4. Place the prepared masterbatch in an oven to dry at 80°C for later use.

Preparation method of elastic membrane

1. Accurately weigh the required quantities of materials for layer A and layer B according to their respective proportions, and mix thoroughly in a mixer for thirty minutes. The ratio of layer A is 70kg LLDPE (7042, Maoming Petrochemical), 20kg POE (8150, Dow) and 10kg open masterbatch, and layer B is 100kg SIS (D1114, Caton);

2. The single-screw extruder is divided into two parts: A extruder and B extruder. The die head is an ABC three-cavity true three-layer die head, in which the A extruder is connected to the A cavity of the die head through a Y-shaped flow channel and C cavity, B extruder is directly connected to die head B cavity;

3. Put the A layer material into the A extruder, and the B layer material into the B extruder. The A layer material and the B layer material are melted and extruded through the extruder to the die to form an ABA three-layer structure, which is cast through a casting roller. Forming, cooling and shaping through cooling rollers, and finally an elastic film with an ABA three-layer structure is prepared.

Example 1

According to the aforementioned elastic film preparation method, the elastic film of the ABA three-layer structure of this embodiment is prepared, in which layer A is composed of 70wt% LLDPE (7042, Maoming Petrochemical) + 20wt% POE (8150, Dow) + 10wt% open masterbatch Composition; B layer is SIS (D1114, Kraton).

According to the above test method, the elastic film prepared in Example 1 was tested for its weight, permanent deformation rate, elongation at break, tensile strength, necking, and thickness. The data are shown in Table 1.

Example 2

According to the aforementioned elastic film preparation method, the elastic film of the ABA three-layer structure of this embodiment is prepared, in which layer A is composed of 70wt% LLDPE (7042, Maoming Petrochemical) + 20wt% POE (8150, Dow) + 10wt% open masterbatch Composition; B layer is SEBS (G1657, Kraton).

According to the above test method, the elastic film prepared in Example 2 was tested for its weight, permanent deformation rate, elongation at break, tensile strength, necking, and thickness. The data are shown in Table 1.

Comparative example 1

According to the aforementioned elastic film preparation method, prepare the elastic film of the ABA three-layer structure of this comparative example, in which the A layer is composed of 70wt% LLDPE (7042, Maoming Petrochemical) + 20wt% PP (HP510, CNOOC and Shell Petrochemical Co., Ltd.) + 10wt % open masterbatch composition; B layer is SIS (D1114, Kraton).

According to the above test method, the weight, permanent deformation rate, elongation at break, tensile strength, necking, and thickness of the elastic film prepared in Comparative Example 1 were tested. The data are shown in Table 1.

It can be seen from the data in Table 1 that compared with Example 1, adding PP to the surface layer has no obvious effect on the elongation at break and the tensile strength is even slightly improved, but the permanent deformation rate is greatly deteriorated and the tensile strength is significantly reduced. The necking at 300% is also noticeably worse. This shows that after the surface layer is modified by POE, its elastic restraint on the elastic layer is lower, so that the resulting elastic film can greatly reduce the permanent deformation rate.

Comparative example 2

According to the aforementioned elastic film preparation method, prepare the ABA three-layer structure elastic film of this comparative example, in which layer A is composed of 70% LLDPE (7042, Maoming Petrochemical) + 20% POE (8150, Dow) + 10% open masterbatch Composition; B layer is 90wt% SIS (D1114, Caton) + 10wt% LDPE (LDPE 0274, Qatar Petrochemical).

According to the above test method, the elastic film prepared in Comparative Example 2 was tested for its weight, permanent deformation rate, elongation at break, tensile strength, necking, and thickness. The data are shown in Table 1.

It can be seen from the data in Table 1 that compared with Example 1, when LDPE was added to the core layer, although the tensile strength was slightly increased and the elongation at break was only slightly reduced, the permanent deformation rate was significantly worse and the tensile strength was significantly reduced. The necking at 300% extension also deteriorates significantly. This shows that adding PE components to the middle core layer will increase the tensile strength of the elastic film, but will decrease the elastic recovery performance.

Comparative example 3

According to the aforementioned elastic film preparation method, prepare the ABA three-layer structure elastic film of this comparative example, in which layer A is composed of 70% LLDPE (7042, Maoming Petrochemical) + 20% POE (8150, Dow) + 10% open masterbatch Composition; B layer is 80wt% SIS (D1114, Kraton) + 20wt% LDPE (LDPE 0274, Qatar Petrochemical).

According to the above test method, the weight, permanent deformation rate, elongation at break, tensile strength, necking, and thickness of the elastic film prepared in Comparative Example 3 were tested. The data are shown in Table 1.

It can be seen from the data in Table 1 that compared with Example 1, when LDPE is added to the core layer, although the tensile strength is significantly improved, the permanent deformation rate is greatly deteriorated, the elongation at break is significantly reduced, and the tensile strength is 300%. The necking becomes more obvious during the period. This also shows that adding PE components to the middle core layer will increase the tensile strength of the elastic film, but will reduce the elastic recovery performance.

Comparative example 4

According to the aforementioned elastic film preparation method, prepare the elastic film of the ABA three-layer structure of this comparative example, in which the A layer is composed of 70wt% LLDPE (7042, Maoming Petrochemical) + 20wt% PP (HP510, CNOOC and Shell Petrochemical Co., Ltd.) + 10wt % open masterbatch composition; B layer is SEBS (G1657, Caton).

According to the above test method, the elastic film prepared in Comparative Example 4 was tested for its weight, permanent deformation rate, elongation at break, tensile strength, necking, and thickness. The data are shown in Table 1.

It can be seen from the data in Table 1 that compared with Example 2, PP was added to the surface layer. Although the elongation at break was slightly reduced and the tensile strength was even slightly increased, the permanent deformation rate and tensile strength were 300%. The necking has significantly worsened. This further shows that the surface layer can be modified by POE to reduce the permanent deformation rate of the entire film.

Comparative example 5

According to the aforementioned elastic film preparation method, prepare the elastic film of the ABA three-layer structure of this comparative example, in which layer A is composed of 40wt% LLDPE (7042, Maoming Petrochemical) + 50wt% POE (8150, Dow) + 10wt% open masterbatch Composition; B layer is SEBS (G1657, Kraton).

According to the above test method, the elastic film prepared in Comparative Example 5 was tested for its weight, permanent deformation rate, elongation at break, tensile strength, necking, and thickness. The data are shown in Table 1.

It can be seen from the data in Table 1 that compared with Example 2, after the POE content in the surface layer is greatly increased, only the tensile strength is slightly reduced, the elongation at break is slightly increased, and the permanent deformation rate and tensile strength are 300%. The necking is quite excellent, but unfortunately there is stickiness between the layers (see Figure 1 and Figure 2, which are the cross-sectional surface morphology of the elastic film of Example 2 and Comparative Example 5 respectively), thus unable to solve the problem of film and The adhesion problem between the films makes it more difficult or impossible to use in practice. This shows that as the amount of POE added to the surface layer increases, the reduction in permanent deformation rate decreases, but the tensile strength decreases seriously, so the optimal amount of POE added is about 20%.

Table 1

Example 3

According to the aforementioned elastic film preparation method, the elastic film of the ABA three-layer structure of this embodiment is prepared, in which layer A is composed of 70wt% LLDPE (7042, Maoming Petrochemical) + 20wt% POE (8150, Dow) + 10wt% open masterbatch Composition; B layer is SEBS (G1657, Kraton).

According to the above test method, the elastic film prepared in Example 3 was tested for its weight, permanent deformation rate, elongation at break, tensile strength, necking, and thickness. The data are shown in Table 2.

Comparative example 6

According to the same formula as Example 3: layer A is composed of 40wt% LLDPE (7042, Maoming Petrochemical) + 50wt% POE (8150, Dow) + 10wt% open masterbatch; layer B is SEBS (G1657, Caton), The elastic membrane with the ABA structure of this comparative example was prepared using traditional split-flow co-extrusion through a distributor.

According to the above test method, the elastic film prepared in Comparative Example 6 was tested for its weight, permanent deformation rate, elongation at break, tensile strength, necking, and thickness. The data are shown in Table 2.

From the comparison of the test data of Example 3 and Comparative Example 6 in Table 2, it can be seen that after using the true three-layer co-extrusion die process, various performance data are more stable and the film weight is more uniform.

Table 2

Effect of surface thickness

In a set of experiments shown in Table 3 below, the components of layer A and layer B (the formula of Example 2) were fixed, and the effects of changes in the thickness of the surface layer (layer A) on the permanent deformation rate, tensile strength, and elongation at break were examined. And the effect of necking when stretched at 300%:

table 3

From the data in Table 3 we can find:

When the thickness of a single surface layer accounts for only 5% of the total thickness and the thickness of the two surface layers accounts for 10% of the total thickness, the permanent deformation rate of the obtained elastic film is 8.1%, which is less than 10%, and the elongation at break and necking after stretching are also It is relatively ideal, which shows that the surface layer of this thickness has relatively little constraint on the elastic layer and does not need to be affected by pretreatment;

When the thickness of a single surface layer accounts for 10% of the total thickness and the thickness of the two surface layers accounts for 20% of the total thickness, the permanent deformation rate of the obtained elastic film is 12.5%, which is slightly greater than 10%. Its elongation at break and tensile back neck Shrinkage also deteriorates slightly, which indicates that as the thickness of the surface layer increases, its constraint on the elastic layer begins to increase;

When the thickness of a single surface layer exceeds 10% of the total thickness and the thickness of the two surface layers exceeds 25% of the total thickness, although the tensile strength of the resulting elastic film increases slightly, its permanent deformation rate is much greater than 10%, and, Its elongation at break and necking after stretching are also significantly deteriorated, which indicates that the surface layer of this thickness restrains the elastic layer too much and requires pretreatment;

After summarizing the data of multiple repeated experiments, the inventor believes that in the elastic film of the present invention, the thickness of each surface layer is preferably 1-5 μm, which preferably accounts for 2% to 10% of the total thickness of the entire elastic film. The two surface layers When the thickness preferably accounts for 4% to 15% of the total thickness of the entire elastic film, the binding of the surface layer to the elastic layer can be reduced to a minimum, and no pretreatment is required during use.

Effect of POE content in the surface layer

The LLDPE (7042, Maoming Petrochemical), POE (8150, Dow) and opening masterbatch in Example 2 were used to prepare layer A, and SEBS (G1657, Caton) was used to prepare layer B. The effect of changes in POE content in layer A on elasticity was investigated. Membrane performance and the impact of production preparation, the obtained data are listed in Table 4.

Table 4

From the data in Table 4 we can find:

When the POE content in the surface layer increases, the permanent deformation rate of the resulting elastic film decreases slightly, the elongation at break increases slightly, and the necking after stretching also decreases slightly. These performance changes are beneficial to the elastic film, but they are The benefits are less obvious;

However, when the POE content in the surface layer increases, the tensile strength of the resulting elastic film is significantly reduced, which is detrimental to the performance of the elastic film;

When the POE content in the surface layer reaches about 30%, signs of stickiness will appear between the layers; when the POE content in the surface layer reaches about 40%, slight stickiness will appear between the layers; when the POE content in the surface layer reaches about 50%, the layers will become sticky. Obvious stickiness appears;

For the purpose of the present invention, interlayer tackiness is unacceptable. Therefore, in the elastic film of the present invention, the proportion of EVA, TPEE or POE in the surface layer can be 5wt%-30wt%, preferably 10wt% -25wt%, more preferably 15wt%-25wt%.

Finally, it should be noted that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, it is still The technical solutions described in the foregoing embodiments may be modified, or equivalent substitutions may be made to some of the technical features. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in within the protection scope of the present invention.

Claims (10)

1. An elastic film having a soft surface layer without pretreatment, the elastic film having an ABA three-layer structure;

wherein the core layer of the elastic membrane comprises SBC materials, and the core layer is an elastic layer for providing elasticity for the elastic membrane;

the surface layer of the elastic membrane comprises low modulus PE as a main body, and is subjected to blending modification by EVA, TPEE or POE, so that the surface layer has soft hand feeling;

the thickness of each surface layer is 1-5 mu m, and is 2-10% of the total thickness of the elastic film, and the thicknesses of the two surface layers are 4-15% of the total thickness of the elastic film, so that the binding of the surface layers to the elastic layer is reduced to the minimum, and pretreatment is not needed when the elastic film is used;

the elastic film has a permanent deformation rate within 12%, an elongation at break of more than 500% and a necking of less than 40% when stretched by 300%.

2. The stretch film of claim 1, wherein the core layer is formed by compounding SBC-like material with an elastomer, wherein the elastomer is EVA, TPEE, or POE, and the ratio of the elastomer to the core layer is not more than 20wt%.

3. The stretch film of claim 1, wherein the low modulus PE in the skin layer is LLDPE, MLDPE, and/or ULDPE.

4. The stretch film of claim 1, wherein the EVA, TPEE or POE in the skin layer comprises 5wt% to 30wt%.

5. The stretch film of claim 1, wherein the skin layer further comprises 5wt% to 15wt% of an open master batch formed from the low modulus PE with the addition of an inorganic powder.

6. The stretch film of claim 5, wherein the open masterbatch comprises 2wt% to 12wt% silica.

7. The stretch film of claim 1, wherein the SBC-like material in the core layer is SI S, SBS, SEBS, SEPS and/or SEEPS.

8. Use of the stretch film according to one of claims 1 to 7 for the manufacture of a garment, a surgical gown or an absorbent hygiene product.

9. The use according to claim 8, wherein the stretch film is used for making a waist band, a cuff elastic or a diaper stretch waist band.

10. A method of making the stretch film of any one of claims 1-7, wherein the ABA three-layer structure of the stretch film is formed using a three-layer co-extrusion die structure.