How to use polyurethane sponge softener to optimize the production process of soft foam products: from raw material selection to finished product inspection
Introduction
Polyurethane soft foam products are widely used in furniture, car seats, mattresses and other fields due to their excellent elasticity, comfort and durability. However, to produce high-quality soft foam products, not only precise process control is required, but also scientific selection and optimization of raw materials are required. Among them, polyurethane sponge softener, as a key additive, has an important impact on the softness, resilience, durability and other properties of the foam. This article will discuss in detail how to use polyurethane sponge softener to optimize the production process of soft foam products from multiple aspects such as raw material selection, production process optimization, and finished product inspection.
1. Raw material selection and proportion optimization
1.1 The mechanism of action of polyurethane sponge softener
Polyurethane sponge softener is a surfactant that mainly improves the fluidity of the foam by reducing the surface tension of the foam system, thereby improving the softness and resilience of the foam. Its mechanism of action mainly includes the following aspects:
- Reduce surface tension: Softeners can reduce the surface tension of the foam system, making bubbles more likely to form and exist stably.
- Improving fluidity: By reducing viscosity, softeners can make the foam system flow more evenly during the foaming process, reducing the bursting and merger of bubbles.
- Enhanced elasticity: Softeners can interact with the polyurethane molecular chain, enhance the elastic modulus of the foam and improve elasticity.
1.2 Raw material selection
In the production of soft foam products, the selection of raw materials is crucial. The following are several key raw materials and their selection criteria:
| Raw Material Type | Select criteria | Common brands/models |
|---|---|---|
| Polyether polyol | Molecular weight is moderate, hydroxyl value range is between 28-56 mgKOH/g, and viscosity is moderate | BASF Lupranol, Dow Voranol |
| Isocyanate | Select MDI or TDI, the NCO content is between 30-35%, and the reaction activity is moderate | BASF Lupranate, Dow Isonate |
| Catalyzer | Select amine or tin catalysts,Moderate reaction speed, avoid too fast or too slow | Air Products Dabco, Evonik Kosmos |
| Frothing agent | Choose water or physical foaming agents (such as HCFC, HFC, etc.), with high foaming efficiency and good environmental protection performance | Honeywell Solstice, Arkema Forane |
| Softening | Select a special softener for polyurethane, with moderate molecular weight, good compatibility with the system, and high stability | Evonik Tego, Momentive Silsoft |
1.3 Ratio optimization
The ratio of raw materials directly affects the performance of the foam. The following are the common raw material ratio range:
| Raw Materials | Rating range (parts by weight) | Remarks |
|---|---|---|
| Polyether polyol | 100 | Benchmark raw materials |
| Isocyanate | 40-60 | Adjust according to hydroxyl value and NCO content |
| Water | 2-5 | Footing agent, the amount of the foam affects the density of the foam |
| Catalyzer | 0.1-0.5 | Adjust according to the reaction speed |
| Softening | 1-3 | Adjust to foam softness requirements |
| Other additives | 0.5-2 | such as flame retardants, antioxidants, etc. |
2. Production process optimization
2.1 Foaming process control
The foaming process is the core link in the production of soft foam and directly affects the structure and performance of the foam. The following are the key control points of the foaming process:
| Process Parameters | Control Range | Impact |
|---|---|---|
| Mixing Temperature | 20-30? | Temperature too high will lead to excessive reaction, and temperature too low will lead to insufficient reaction |
| Agitation speed | 1000-3000 rpm | The stirring speed affects the uniformity of the bubbles, and too high will cause the bubbles to burst |
| Foaming time | 5-10 minutes | The foaming time is too short, which will lead to uneven foam density, and too long may lead to foam collapse |
| Mature temperature | 50-80? | The maturation temperature affects the degree of crosslinking of the foam. Too high temperature may cause the foam to harden |
| Mature Time | 2-4 hours | The maturation time is too short, which will lead to insufficient foam strength, and too long may affect production efficiency |
2.2 How to add softener
The addition of softener has a significant impact on foam performance. Common ways to add include:
- Premix method: Premix the softener with polyether polyol in advance, and then perform a foaming reaction. This method can ensure that the softener is evenly dispersed in the system and is suitable for large-scale production.
- Post addition method: After the foaming reaction reaches a certain level, add a softener. This method is suitable for occasions where there are special requirements for foam softness, but it is difficult to operate.
2.3 Process Optimization Example
The following is a typical soft foam production process optimization example:
| Process Steps | Pre-optimization parameters | Optimized parameters | Optimization effect |
|---|---|---|---|
| Mixing Temperature | 25? | 22? | Reduce the reaction speed and reduce bubble burst |
| Agitation speed | 2000 rpm | 2500 rpm | Improve bubble uniformity and reduce bubble density differences |
| Software addition method | Add method | Premix method | Improve the uniformity of softener dispersion and improveFoam softness |
| Mature temperature | 70? | 60? | Reduce the maturation temperature to prevent the foam from becoming harder |
3. Finished product inspection and quality control
3.1 Physical performance test
The physical properties of soft foam products are an important indicator for measuring their quality. The following are common physical performance testing items:
| Test items | Testing Standards | Qualification Range | Remarks |
|---|---|---|---|
| Density | ASTM D3574 | 20-50 kg/m³ | Often the density may lead to insufficient foam strength, and too high may affect softness |
| Resilience | ASTM D3574 | ?40% | Low resilience may shorten the service life of the foam |
| Tension Strength | ASTM D3574 | ?80 kPa | Tension strength is too low may cause the foam to tear |
| Tear Strength | ASTM D3574 | ?2 N/cm | Tear strength is too low may cause the foam to burst |
| Compression permanent deformation | ASTM D3574 | ?10% | Overlasting compression deformation may cause the foam to lose elasticity |
3.2 Chemical performance test
The chemical properties of soft foam products directly affect their durability and safety. The following are common chemical performance testing items:
| Test items | Testing Standards | Qualification Range | Remarks |
|---|---|---|---|
| VOC content | ISO 16000-6 | ?100 µg/m³ | VOC content is too high and may be for peopleHealth causes harm |
| Formaldehyde emission | GB 18587 | ?0.05 mg/m³ | Excessive formaldehyde emission may cause harm to human health |
| Flame retardant performance | GB 8624 | Level B1 | Unqualified flame retardant performance may lead to fire hazards |
3.3 Finished product inspection process
The following is the finished product inspection process for soft foam products:
- Sampling: Randomly sampled from the production line to ensure that the sample is representative.
- Physical Performance Test: According to standard testing methods, the density, resilience, tensile strength, tear strength, permanent compression deformation of the sample is tested.
- Chemical performance test: Test the VOC content, formaldehyde emission, flame retardant properties of the sample.
- Data Analysis: Compare the test results with the pass range to analyze whether there are quality problems.
- Feedback and Improvement: Adjust the production process in a timely manner according to the test results to ensure stable product quality.
IV. Frequently Asked Questions and Solutions
4.1 Uneven foam density
Problem Description: The density of foam products is unevenly distributed, and the density in some areas is too high or too low.
Possible Causes:
- The stirring speed is uneven, resulting in uneven bubble distribution.
- The amount of foaming agent is inaccurate, resulting in uneven foaming.
- The softener is unevenly dispersed, affecting the foam structure.
Solution:
- Adjust the stirring speed to ensure even distribution of bubbles.
- Accurately control the amount of foaming agent to ensure uniform foaming.
- Add softener by premixing method to ensure uniform dispersion.
4.2 Inadequate foam resilience
Problem Description: Foam products have poor resilience and recover slowly after pressing.
Possible Causes:
- Inadequate amount of softener is used, resulting in too low elastic modulus of foam.
- The maturation temperature is too high, resulting in excessive crosslinking of foam.
- The amount of catalyst is used too much, resulting in too fast reaction and unstable foam structure.
Solution:
- Increase the amount of softener to improve foam elasticity.
- Reduce the maturation temperature and avoid excessive foam crosslinking.
- Reduce the amount of catalyst and control the reaction rate.
4.3 Low foam tear strength
Problem Description: Foam products are prone to tear and have a short service life.
Possible Causes:
- The molecular weight of the polyether polyol is too low, resulting in insufficient foam strength.
- Insufficient isocyanate usage, resulting in low foam crosslinking.
- The softener has poor compatibility with the system, affecting the foam structure.
Solution:
- Select polyether polyols with moderate molecular weight to improve foam strength.
- Increase the amount of isocyanate to increase the foam crosslinking degree.
- Select a softener with good compatibility with the system to ensure the stable foam structure.
5. Future development trends
5.1 Development of environmentally friendly softeners
As the increasingly strict environmental regulations, the development of environmentally friendly polyurethane sponge softener has become a future trend. Environmentally friendly softeners should have the following characteristics:
- Low VOC content: Reduce pollution to the environment.
- Biodegradability: Easy to degrade and reduce the impact on the ecological environment.
- Non-toxic and harmless: Ensure that it is harmless to human health.
5.2 Intelligent production process
With the advancement of Industry 4.0, intelligent production processes will become the mainstream trend in the production of soft foam products. Intelligent production processes can realize the following functions:
- Real-time monitoring: Monitor various parameters in the production process in real time through sensors to ensure process stability.
- Automatic adjustment: Automatically adjust process parameters according to monitoring results to ensure product quality.
- Data ScoreAnalysis: Through big data analysis, optimize production processes and improve production efficiency.
5.3 Application of high-performance softeners
As consumers increase their performance requirements for soft foam products, the application of high-performance softeners will become a future trend. High-performance softeners should have the following characteristics:
- Veriodic: It can not only improve the softness of the foam, but also enhance its durability, flame retardancy and other properties.
- Compatibility: Compatible with a variety of raw material systems, suitable for different types of soft foam products.
- Stability: It can maintain stable performance in harsh environments such as high temperature and high humidity.
Conclusion
By scientifically selecting raw materials, optimizing production processes, and strictly controlling finished product inspection, the use of polyurethane sponge softener can effectively improve the performance of soft foam products. In the future, with the development of environmentally friendly and high-performance softeners and the application of intelligent production processes, the production of soft foam products will usher in broader development prospects.
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